I have the same shield and arduino, wired in the same way as this link: http://i.stack.imgur.com/PfIu8.jpg
And I am using the same code as this link: http://tronixstuff.com/2014/01/08/tutorial-arduino-and-sim900-gsm-modules/
I am using an external power supply to power the GSM shield and my PC to power the arduino. The NetLight on the shield flashes once every second for 10 seconds then once every 3 seconds, so it is connecting (vodafone PAYG) ok, but I cannot get it to work
I know this is not the official arduino GSM shield.
I am new to arduino