I have an Asterisk box with local US DID, that authenticates the users with their caller ID then does some IVR and then vo-ip dials out to overseas phone numbers over SIP.
Recently there are some users (interestingly they are all t-Mobile users) complaining that they have received very high long distance calling charges on their phone bills. The confusing part is that, they didn’t have to enter the overseas phone numbers during the IVR, so even if the complaints are true, I don’t understand how t-Mobile carrier system would know, where to the call is being made by Asterisk box.
I have thousands of users, and this is happening very rare , but when it happens its always with t-Mobile users.
I suspect that is a commercial issue with whoever operates the T-Mobile brand in your country.
It is not that uncommon for more traditional operators to block your sort of service and making a high charge seems a plausible alternative. A precedent for differential charging is that UK landlines phones often do not get discounts (e.g. exclude from free allowances) when calling ISPs (although there can’t be that many dial up ones left).
They don’t need to know that the final number will be international, only that the call is being made through a service that is primarily used for that purpose.
You might want to investigate whether there is any legislation, in your country, that would allow such practices as anti-competitive.
I would like to know if I am not able to connect directly to T-Mobile with asterisk (instead of the router), what kind of interface card would I need to plug the asterisk box into the phone jacks on the router? Any suggestions really appreciated.
Is is possible that you have reinvite turned on? I may be wrong, but my understanding is that this will cause asterisk to tell the connected parties to connect to each other directly- thus bypassing asterisk. So its possible that your asterisk is telling your user’s cell phone to connect to the overseas party directly - and as such, incur long distance charges.
The option that used to be called “canrinvite”, but is now called “directmedia”, only works within the SIP part of the call, and only affects the media streak. It would be weird for someone to charge for a change in the media stream, especially as the likely result is a reduction in their costs.
Although there is some scope for ambiguity, I believe the configuration described here was ISDN on one side and SIP on the other, so direct media would have been impossible.