VoIP provider and surcharged numbers


We are building an application with asterisk and it uses one (later various) remote voip providers. For now we are using terrasip. We will have to pay all our clients communications

The problem is that we can’t allow our clients to make surcharged calls so we must block them. They can only call landlines and mobile phones all around the world.

We thought of an international numbering plan that contains all authorized prefix that are not surcharged. Maybe a list of the international surcharged numbers would be easy to get ?
Maybe you know a VoIP provider that automatically blocks surcharged numbers ?

We are still looking for a solution, is there anyone who has already faced the same problem ?

Thank you very much for your advices.

Vincent Roye.

I doubt there is universal rules/solution. I am using call rate table (provided from every provider) and price of call.
It is not perfect solution but it could handle most of cases.

Thank you for your answer. Do you know any provider who has a list of surcharged number, in order to block them ?

We are also planning to use the call rate table but we really can’t allow expensives numbers.