Default EXT Network issues

Hi, looking for some assistance (again). I have had issues with getting the correct data network on my phone.

The phone is a HTC One M7, I bought it sim free in the UK.

I have put a virgin mobile sim card in the phone and the only network that comes up is EXT, when I try to connect it states that my SIM is not allowed a connection to this network. This only happens where I stay which is out of town. I had the same issue with a TELUS sim too. The only one that works is a Rogers one but I only get EDGE.

In the city they all work fine giving me LTE or HSPA+.

Please could somebody assist?