Hi there and welcome
You mean it just keeps hoping between the sim ports Steve on its own?
Ok, remove the battery and wait 5 minutes, put the battery back in, turn it on and tell me how it then performs please
ok, let me know the results please.
Can you go to Settings, Applications Manager.
Swipe to the list all and locate Google Services Framework
Press it and press clear data.
Once done, restart the phone and tell me if it now connects please.
its under the list ALL but if you did a factory reset then that is the next step anyway.
This means it is not software related.
If you put the sim card in the second port, does that get connected?
It is but there are three causes for it, either the firmware or the mainboard as you ruled out the sim card as the issue as it works in another phone. There the only reasons for this.
I was hoping at least the 2nd port was working, but if this is not the case it means the mainboard has been damaged and its not able to talk to the network. It will likely be the antenna on it
Your welcome Steve, if you need anything else, please let me know
And please remember the service rating via one of the stars at the top then submit