Phone says searching - no network

Used my Iphone 5s few days ago in the morning and made few calls, all working fine. And then when I tried making another call it said call failed. And then I see it says searching on the top left. So theres no network connection. Since then its still been searching.

Following steps have been tried but still not fixed.

1) reset/hard resetting the phone.

2) toggle airplane mode on/off several times.

3) reset network settings.

4) Checked sim-card in different phone and working fine.

5) Tried another sim-card in this phone and still saying searching.

6) Connected to i-tunes did a full backup and restore.

After completing step 6, As the phone is wiped, its now not activating the phone as its still saying searching. (cannot find network, hence not activating as it needs to read the sim card network)

I am not convinced it can be hardware related as I was using it fine in the morning and have never had any issues with it, nor did I drop it or anything. Really confused at the moment and quiet stressed out. Any help will be much appreciated.