Iphone 5 Signal Drop/ Cant make or receive calls 3 Network UK

Hi, is anybody else experiencing this issue?

Recently I have had people telling me they were trying to call me but my phone did not ring at all and it had full signal as far as i can tell - I have also tried calling people and getting absolutely nothing happening. Tried to phone my phone from my girlfriends iPhone 4s (ios6) and it wouldnt ring... also reversed the process and couldnt call her, texts regularly fail to send as well... this problem seems to be intermittent.

I live in Edinburgh and as far as im aware Three has good coverage here, my girlfriend and her mum both have iphone 4s's and are on the 3 network and do not have this issue so this makes me think it is related to the iphone 5 in some way. I have also noticed when i do have a conversation with someone the clarity is not very clear.

Has anybody had any similiar experiences/ know what i should do? - The closest Apple shop is 50 miles away so it's a last resort taking it to a genius bar!

Have tried all the usual steps, turn on/ off aeroplane mode, soft reset, turn phone on and off, resent network settings etc and the problem is still there - I have done everything short of a full restore!

Iphone in question is White iPhone 5 32GB running iOS 6.0.1

Thanks in advance.

Lee