Iphone 4 - 32gb FAULTY +

Here i have an iPhone 4 - 32gb. It is in great condition. Basically like new. Has a screen protector on front. However, there is a NO SERVICE/NO SIGNAL fault. I am not really sure why this has happened. Previously on o2 network I have been told this phone works outside of UK so could turn out be a good bargain for someone. Will post if I get paid into PAYPAL first!! NO scammers!! Prefer cash on collection. Any more questions just ask.