it works perfectly
What functionality is working? I would suggest strart with SMS instead of voice calling to make sure you can interact with the GSM network. Initially I used this utility called gammu
gammu sendsms* TEXT 082111978168 -text "Halooo
And also try AT commands from GSM modules manufacturers documentation. There can be small variations between modules.
For calling I used this one but there was another one to put the modem into right state for calling.
ATD+31111111;
When you make call you will need to forward voice from your microphone to modem and from modem to your speaker. At that stage you are having normal phone like voice call.
Then you can help me out to make it work on Android.