This solution will be enjoyed by many of your customers who have subscribed to your low-rate telephony services. SMS texting is fashionable, universally available and simple and there is a growing trend to use SMS in various information and micropayment services.

Likewise, one of the easiest ways to request a callback is by sending an SMS. In those situations when the customer cannot use the web, his assigned ANI telephone or any other working touchtone telephone then the authorisation by SMS is in most cases still available.

The customer submits via SMS this data:
(1) source number (very likely the caller's mobile phone number);
(2) destination number (the callee's phone number),
(3) PIN (the secure identifier issued by you).
The callback server analyses the SMS for correctness, then dials the source number. After hearing the account balance information, the customer is put through to the destination number.

Features:

Technically the SMS callback authorisation server can be maintained in an internet location different from the one where you house your main processing system. Communication between the two is secure thanks to 3DES (triple data encryption standard), which safeguards against PIN theft.