hiya followed Ifixit to repair Iphone 4s all went fine but had "scanning" no service" on, messaging, wifi and phone calls worked fine so knew nothing could be seriously wrong checked battery connector spring clip was touching rear cover all ok tried setting time n date(was at 1 jan 1970) that dod'nt work, re booting never done trick turned on 3G and hey presto it stopped scanning and found carrier(O2 uk) and auto time n date worked turned off 3G and all ok now hope this helps someone else best regards
Darkman