Stuck in "searching..." for network

My iPhone 6 Plus was recently unlocked (two days ago) and I've since been trying to get it to connect to the network. So far I've tried:

- Rebooting the phone with the new sim card in

- Force rebooting the phone with the new sim card in

- Just popping the sim card in when the phone is on

- Connecting to iTunes via USB

- Doing a full restore via iTunes

- Resetting the network settings

- Doing a reset via settings

All the IMEI checks come back clean so no blacklists or anything but I still cant get any reception or network connection. Is the only possible option the antenna now?

Thanks