iPhone 4S 16 GB - Can't dial/text anymore?

Hi there!

I've been dealing with quite a handful iPhones over the years but this problem I have never encountered before. This weekend a family member lost her iPhone 4S 16 GB and we thought it was stolen, so we reported it missing and locked it using iCloud/Find My iPhone.

Now we've found it again under a car seat but after unlocking it we cannot dial/text with the phone anymore. It can find the cell phone provider and writes "3G" but all the five little round dots are all blank. (As in there is no signal)

When trying to dial a phone number the dial options doesn't even come up, the phone simply hangs up right away and logs it as a failed call. I've thought of the antenna but this seems more of a software issue with this behaviour.

I've tried with 3 different SIM cards and none of them work using this phone. On my other iPhone they all work and have plenty of reception. I've also tried a complete reset and a complete restore of the phone without any succes.

Unfortunately the phone is running the latest 8.1.3 version of iOS, so I cannot try a firmware update. (Or downgrade due to Apple policy)

I've recorded a video to explain the issue more clearly.

https://www.youtube.com/watch?v=rf_LFPVfgLE

I have never ever seen anything similar to this. Any ideas?! I'm totally lost here.

Regards,

Brian