VoIP GSM. A VoIP GSM Gateway connects a VoIP service to a GSM/CDMA service, so that a customer can have VoIP coverage without the cost of a traditional POTS line. A VoIP GSM Gateway from Edge Telecom is a cost-effective way for VoIP providers to add coverage without the cost of a traditional POTS line.

https://voipgsmgateway.blogspot.com/2022/01/who-is-best-provider-in-voip-gsm.html
https://medium.com/@gsmgateway972/m-best-gsm-gateway-provider-delhi-ncr-afc1167e16d4