I had to look this up for a friends phone 'searching' had suspected the antenna had ben unplugged but it was on OK. I noticed time was not changing.
phone had already been left alone for more than 10 mins
I tried Reinsert sim = nothing
I tried reset = nothing
I tried plug it in = nothing
I tried calling out = nothing
i tried calling the phone = nothing
I turned on Wi-Fi & connected = time change instantly, then the searching changed to the network & full signal.
:-) thanks to the others that help on here. you are legends