Getting GSM shield to call then hang up

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

Any help?

Thanks

See link in my signature.

Depending on signal quality a 1 amp supply may not be enough.

Thanks, I'm just reading your link now.

I am using a 12V 26AH battery

OK, so I tried the code in the link you sent me - the first piece of code. I can successfully send the AT command, but I am not getting any reply in 5 minutes. Does this mean that there is a problem with the connections between the shield and uno? Because I have tried all combinations of the RX and TX wiring

Thanks for your help

Why don't you just plug the shield into the Arduino instead of wiring it up like that?

Anyway, you 'send' the AT command, it should respond almost immediately?

The shield I have doesn't have pins at the bottom for plugging it in! So the only way is to use jumper wires.

Ok, well I don't get any reply, strange.

You posted a photo of a shield. So what you are saying is that isn't the one you actually have?

That picture isn't mine, but my shield looks exactly like the one in the picture

In that case why not connect D7 to D7, D8 to D8 and Gnd to Gnd?

That's what I'm doing...