Connecting with A-Z VoIP Vendors

9 min read


In this post, we will provide an overview of three prepaid A-Z VoIP vendors and go over their self-help portals to show how to connect with them.

We selected three A-Z vendors that accept online registrations and are quite easy to start using:

The following guidelines are the aggregate result of these three vendors and are not presented individually. This has been done to illustrate the usual workflow of how to connect to similar A-Z vendors and so as not to fixate on the vendors we chose as our test-base.


Sign-up and registration are easy and straightforward. You agree to the online terms & conditions, enter your details, select a password, receive an email, and press on the confirmation link.

At this point, you are usually done. When I completed registration, however, I received a message that IDT wanted to talk with me over Google Meets. I am not sure if I got “lucky” here or if this is their usual way of handling all new registrations at IDT Express.

Contact Information

When you log in to the self-help portal, there are some settings that must be filled in before anything else can be done.

Usually, these include contact information details, such as company name, address, phone, email, and VAT.

Afterwards, contacts may be divided based on the function or nature of the problem. For example, you may need to enter Main Tech contact details or create separate email notifications for things like rates or general, technical, and billing emails. Based on your company size, this could mean one email for all of the fields or different emails for each of them.

Rate Information

It is important to note the currency in which the rates are presented and in which your balance with the vendor is kept. Some vendors allow for only one currency; for example, IDT Express only accepts USD. Voicetrading allows EUR and USD. The currencies accepted differ for every vendor and should be noted to avoid any mistakes in the future.

A-Z vendors usually provide several different rate plans based on the quality-price ratio. The worst quality usually comes at the best price, decent quality at a moderate price, and the best quality at the highest price. Make a note of these plans and decide which ones you will be using.

In addition, it is important to notice the special rate markings, such as a rate of -1.00000, which signals a “blocked location.” Because there is no unified standard to describe the tariff format, each vendor can have different rules that determine how they mark their rates. It is crucial to make a note of this and configure your system properly to avoid a bad rating later.

Vendors provide rate updates at different times. IDT, for example, sends updates each week. Voicetrading provides theirs at the end of the month. Check the schedule and take care to process these updates accordingly in your system.

How can you get a better rate? Usually, when you generate a lot of traffic, you gain leverage to negotiate for better rates. For individual rate requests, it is best to contact your salesperson. If you don’t have one, write to the company to request the details of such a salesperson (who is usually called an account manager.)


Some vendors allow you to configure several security, or so-called “anti-hacking,” features. You should take advantage of these features if they’re available because they can be really useful and help you to avoid a big loss in the case of malicious activity.

Max spend per day is one such feature. With this, you can enter how much you can spend in 24 hours and any excess traffic will be blocked.

Max rate/stop rate per minute prevents you from calling expensive destinations. Because of the various prefix mismatches, some people do so-called “cherry-picking” in the rate plans, looking for badly configured prefixes and using them to dial expensive destinations when the rate plans charge them peanuts for such calls. This is just one way that people may exploit your mistakes. With this security feature, however, if you set a stop rate at $0.40 and a call comes from your switch to Cuba Mobile with a rate of $0.5985, the call will be rejected. Max rate is therefore a useful feature to help safeguard your account in case of a hacking incident.



To connect your server, you need to enter its IP address into the portal.

After adding an IP address, the vendor will open access on its firewall for it and allow the connection on their switch. It often takes some time for vendors to complete such a procedure. For some of them, it may take up to 1 to 2 hours. Check with the vendor and don’t panic if traffic does not start to flow instantly.

Shared or dynamic IP addresses are usually prohibited. Do not use them.

Vendors do not usually put any limit on how many IP addresses you can have.


Some vendors give you a small amount of money to make a few test calls and incentivize you for using their services.

In order to use a service to its full potential, however, you must properly fund your account by making a transfer.

Vendors accept different payment methods. The usual ones are credit cards, PayPal, and bank wire transfers. Some vendors also accept Western Union, Crypto, and a few other exotics.

A credit card needs to be confirmed. Vendors may require a copy of your latest credit card statement, copies of the front and back of the card (blanking out the middle 8 digits), and a government-issued photo ID. When adding a new credit card to your account, the verification process can take 1 to 2 business days. This is done to avoid credit card fraud.

PayPal is usually offered to clients with the highest trust ratings because of the pro-client leaning of PayPal’s policy in which the client is always right no matter what and refunds are issued without questions asked. Thus you often have to earn the right to use PayPal with vendors. Do not assume you will be able to use it from the start.

Some vendors may charge you additional fees for using different payment methods. Fees can vary but are usually around 2% to 3%.

Auto-recharge payment is an optional feature that charges your credit card automatically when your balance is low. If you have the auto-recharge feature enabled, your account will never run out of funds. You can set the amount to charge and the threshold value. We encourage you to take advantage of this option for a worry-free account.

Usually there is a smallest amount you can top up, which may be around $50.

The Low balance notification option sends a daily alert to your billing email group when your account balance drops below the set threshold. It is strongly recommended that you use this feature and set the threshold to a level that allows for enough time to post and process a payment. That way, you can avoid a service interruption.

Vendors may send invoices over email or allow you to download them from the web. It is interesting to note that IDT Express does not issue invoices for the prepaid accounts for some unknown reason. Instead, they recommend that you use a combination of the monthly statement and your payment history details to “reconcile your books.” This may be unacceptable in some countries with strict accounting laws, so be sure to take this into account.

If you have a VAT code, make sure you provide proof of it to the vendor, so they can exempt you from the VAT tax. Usually, the vendor provides information on how to do that online. If they do not, contact them directly and complete this procedure before making any transfer to them. When they already have your money, the VAT verification and refund process usually takes longer. For EU companies, it is usually enough to point the vendor to the site where every company in the EU can be checked for VAT code validity.

Technical Details

Check vendors’s server’s IPs to see where you should send the traffic.

If there are several POPs, ping and find the closest to your switch to ensure the best quality.

Authentication via IP is the de facto standard. Authentication over username and password is very rare. Nevertheless, Voicetrading offers it.

Check tech prefixes for different plans. Make a note of them and configure them in your switch to properly choose a plan.

SIP should be used as a protocol. If you need such exotics as H323 or something even rarer, you will have a hard time finding an A-Z VoIP vendor that will support it.

The main codecs in this business are G729 and G711A/G711U (alaw/ulaw). Vendors usually support some others, such as G723, G726, iLBC, and GSM. Make sure, however, that they have the G729 and G711 as that is usually enough. There are several variations of G729 codec (G729A, G729AB), so when in doubt, look for G729A.

Fax support varies from vendor to vendor. The vendor will usually tell you that they support T38 for faxing but cannot offer any guarantees and only offer their best effort, maybe even with G711 fallback. Fax as a means of communication is dying and nobody cares about it too much. In our experience, trouble tickets with the word “fax” in the subject line automatically have gotten lowest priority.

Channels or ports are the terms that define how many simultaneous calls you can send. Some vendors give you limited ports/channels at the start and you should write to them, ask them, and even beg them to give you more. Others will give you a high amount of ports from the get-go and off you go. Voxbeam requires that you keep a minimum deposit on your account equal to the number of channels that you have open.  This also means that your calls will be stopped when your balance reaches the amount that is equal to your channels. It may sound weird but be aware of such nuances with different vendors.

Number format is almost identical everywhere and uses the E164 standard. Some vendors, for some weird reason, may ask you to add a + sign in front of the E164 number. Take note and configure your switch accordingly.

PAID (P-Asserted-Identity)/RPID (Remote-Party-ID) support is vendor-dependent. Do not expect all of them to follow RFC ( and consult the documentation before using these headers.

SIP RE-Invites may be imposed by some vendors. IDT Express has a 15-minute SIP session timer set on all incoming SIP traffic, which means that they will send a SIP re-invite to your switch 15 minutes into the call. Please make sure that you are allowing SIP re-invites on your switch. If you are not sure how to enable SIP re-invites on your specific switch, please reach out to your vendor. Otherwise, the call will drop after 15 minutes.

PRACK, SIP OPTIONS, and DTMF support will be different for each vendor. If they are crucial for you, be sure to consult with the provided documentation or ask the vendor about it directly.

By default, IP Ranges for RTP are not limited and are accepted from the whole internet. Some vendors, however, may require you to specify from which IPs media will come. Make sure you do that.


Vendors provide technical help and troubleshooting at different times. Only the largest ones provide equal support 24/7. That means that in the off-hours, only critical problems will be solved by the technicians and all other questions and issues will be put off until working hours. Make a note of when support is provided and which channels are used (such as email, phone, or an online system).

It is also worth it to find out the answers to the following questions:

  • Is there someone able to work on my tickets on nights and weekends?
  • How do I open a trouble ticket?
  • How can I find the status of an existing trouble ticket?
  • What is the normal turnaround time for a trouble ticket?


CDRs are the main reports that you can get from the vendor. They are usually downloadable from the portal in the CSV/XLS format when unzipped.

Some vendors allow you to view them online.

Notice which time zone your CDRs are in. It is very common to provide CDRs in UTC (GMT) time. This allows for easy CDR matching in the case of disputes.

Because of the large storage requirements needed for these files, vendors only store CDRs for a limited time, such as 7 days. Should you require these files for future reference, it is recommended that you save them locally to your computer.

To save space, vendors usually only give you CDRs that show completed calls. All failed calls are discarded.

Other examples of reports that can be provided from vendors are:

  • Summary CDRs
  • Capacity usage for the week
  • Capacity usage for the month
  • Financial statements
  • Reconciliations


As you can see, the initial configuration process for an A-Z vendor can be quite lengthy and it is important to configure it properly. Here is a short checklist of what to do, what to note, and what the most important details are:

Fill in company details.  
Fill in different contact details.  
What currency are your account and rates set in? USD/EUR
What different plans does the vendor offer?         Cheap/Mid-range/High-quality
Are there any special rate markings? Yes     No
How often are rate updates sent?  
What is the contact information for your account manager?  
Set your max spend per day. Done     Not Available
Set your max rate/stop rate per minute. Done     Not Available
Enter your own switch IPs.  
Are credit cards supported? Yes     No
Is PayPal supported? Yes     No
Are bank wire transfers supported? Yes     No
Other payment methods:  
Fees on each payment method:  
Enter your credit card info.  
What are the requirements to confirm your credit card?  
What is the smallest amount you can top up?  
Set the low balance notification. Done     Not Available
Save a link where you can get your invoices.  
What is the procedure for VAT confirmation? Fulfill it.  
Technical Details  
Vendor’s IPs:  
Which IP you will use (if there is more than 1).  
Write down the tech prefixes for the vendor’s plans.  
Make sure SIP is supported (just in case). Yes     No
Is G729/G711 supported? Yes     No
What other codecs are supported?  
Is there fax support? Yes     No
How many channels/ports are there initially and what is the procedure to increase them?  
Number format for Destination/Source (Caller ID):  
Is there PAID/RPID support? Yes     No
Is there SIP re-invite support? Yes     No
Is there PRACK, SIP OPTIONS, DTMF support? Yes     No
Can IPs for media be from anywhere or do they need to be registered?  
Working hours:  
Ways to reach them:  
Time zone:  
How long are CDRs stored?  
Can you get CDRs for failed calls?  
Link for quick access to CDRs:  
Other useful reports:  

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