How to get audio stream from GSM modem

I am working on a IoT Project with a GSM Module. What i am trying to achieve is you can insert your SIM in the GSM Modem and if you receive a Phone call if will automatically forward the call to an APP (Connected to a server and listen to a PORT) and from APP you can answer the call.

Any help will be highly appreciated.


in a different project I also tried to forward a phone call, but with no success.
Therefore I am also interested in such a solution.