USSD Call Back
USSD Callback is a VPMN-independent solution that enables low-cost voice calls for postpaid and prepaid subscribers. The solution can be activated for all roaming party networks or only on selected networks.
The USSD Callback solution is available in two variations; Conventional USSD Callback – Subscriber sends a USSD string which includes the dialed number (B-Number) or Seamless USSD Callback – a Java-based applet which is installed on the SIM card. Both solutions can be implemented over INAP or SIP.