Call-back services are used in areas where it may be difficult due to regulatory conditions to provide either VoIP services or calling card services.
Principles of Call-back
The principle of call-back is that it is often cheaper to phone into a country rather than phone out using the incumbent operator. It also works on the principle that calls are not charged if they are not answered.
A customer calls a trigger number, which is never answered, so no charge. This triggers a call-back from the A2Billing platform which is answered by the customer who is then presented with secondary dial-tone to make their call.
A2Billing supports ANI call-back and web call-back, and DID call-back can easily be configured.