[SOLVED] Testing Arduino GSM Shield with Arduino Mega 2560 R3

Hi, Trying to test new official Arduino GSM Shield with Arduino Mega by uploading example codes from the website (TestGPRS, TestWebServer, Send/Receive_SMS, etc). However, codes are uploaded easily but as I open the serial monitor only the first lines are being printed (Connecting GSM Network...., etc) and nothing comes up (waited up to 30 mins), or when I try to send SMS its being printed that transaction is completed, but i don't get any messages. Even If i try to put the country code in the beginning.

So, what do you think guys might cause me problem? Thanks in advance For sure: 1) I am using GiffGaff mobile network provider, which operates on O2 operator. 2) I have connected 1 Gb data allowance + unlimited sms 3) I am in United Kingdom 4) I use Mac

Guys, I have solved this issue with the help of some good guys. Check this out http://arduino.cc/en/Guide/GSMShieldLeonardoMega