Only Android app dev with experience please.
We need a soft that convert incoming calls from Internet (via WIFI, 4g, 3g etc..) to be sent to the GSM network via the Local SIM card.
1. This app should work as a SIP client with any Sip proxy server in the cloud
2. The APP will use SIP proxy information to connect: username/password and Proxy IP@
3. This will create a tunnel so call sent from the server will be sent to the GSM network automatically.
4. Take a look at the schema attached.