I have Arduino Mega 2560 and GSM/GPRS SIMCom SIM900 shield.
I uploaded the MakeVoiceCall code included in GSM library, mounted the shield on Mega and connected pin 2 with pin 1. I have SIM card installed into the shield. BUT when I open the monitor I only get the response "Make Voice Call", it seems that the program get stuck at statement (gsmAccess.begin).
the SIM card doesn't have PIN number.