Iphone 4 brilliant Cond cheap due to minor issue -

Hi There. I want to sell my iphone 4 16 gb black in excellent cond just bcoz it was on o2 and ios 4.1. i tried to upgrade it on ios 5 it is now showing no service. I had it 2 days before.If someone who want to fix it or a serious buyer.no time wasters plz.cash on collection only. Thanx