Iphone 5 keeps searching network problem....

My iphone 5 today suddenly started started searching network,

I took out the SIM card , it still kept searching for network instead of saying no sim or no service.

I reset network settings, then all settings, turned phone on off several times, put back sim in, hard reset it etc.

I haven't restored it from itunes that I will do next but I am wondering if any one had simlar problem.

Taking SIM card out should changed it to no sim or no service but it doesn't do that so that is weird. It doesn't matter which location because I was in my car when it started searching and I came back home still the same.

Another thing is it doesn't give me an option to select carrier manually as that option has disappeared from the settings.