Configurations
of GSM/VoIP networks allow the service providers to avoid the local Wired
Public Switched Network (PSTN) in communication with a GMS mobile handset. As a
result, the high rates charged by telephone companies are avoided.
The service often seen at different sites works in such a way that you
need to enter your telephone number in a special window and after some seconds
you and the company representative will receive a call, which will allow you
communicating.