SAMSUNG GALAXY NEXUS GOOD CONDITION NO SIGNAL / SERVICE ?

Bought from car boot sale a while back, but suddenly it is not making calls, all other functions are still running, I was using it on O2 network, not sure if it is unlocked, just the phone is available, it is in mint condition and i had a screen protector put on to protect the screen from scratches. Buyer must collect from HIGH WYCOMBE. CASH ON COLLECTION ONLY. PLZ REMEMBER NO SIGNAL/SERVICE FAULT.