jarwulf:
Grumpy_Mike:
Any you like apart from 0 & 1 which are used for the hardware serial port.Are you familiar with the GSM library athttps://github.com/MarcoMartines/GSM-GPRS-GPS-Shield/blob/GSMSHIELD/doc/List.txt
When I decomment the ........................
So what, that does not change my answer. You can use any pin you want. What you can not do is change the pin in software and hope that it will magically change the wiring in the hardware.
So if you change the software you have to change the hardware.
Pin 2 is currently being used as an input for another attached device and is soldered through a header for a secure connection.
Remember pins 2 & 3 are the ones that can directly trigger interrupts, so if your device software needs this then you will have to do some rewriting to use another interrupt mechanism.