dont know if you all know about this but it's new to me, today, had a text off O2 for an app to download called TU go and basicly what it does is , if you havnt got a phone signal but have got a wifi signal you can still use your phone as normal , all free the calls just come out of your allowence, well iv done it and it definitely works , never got a signal in the house but my phone works now, havnt tried it anywhere else yet but so far so good, another thing you can register up to 10 devices, I have another phone on three, and that doesn't work any where near here but have registered that one as well and that now works in the house as well, probably some downside to it but can't see one yet.