apple iphone 4 16gb great condition slight fault +

i have a iphone 4 16gb that is in excellent condition. with hardly a mark on it. iv had it for about 4 months and it worked fine until the other day when i updated to the new 6.0 software. it updated fine but for some reason wont register me on the network my 3 sim card activated the phone on setup but now just shows no signal maybe software fault maybe network. not sure so am selling as spares or repair everything else works fine all app store and wifi and music.can send txts through whatsapp and call on viber so can still be used as a great phone comes with box charger and headphones £150 ono call for details or txt for immediate answer thanks