Sorry to hear of your difficulties.
I am in an equally barren network area in the New Forest. Mobile network signala are very weak and/or non-existent, hence the need for wi-fi calling.
Also our BT Broadband connection is very fragile and misbehaves with the weather - we still have copper wires on poles!
For the time being the wifi calling is working and I use it all the time, even with the landline doverted to mobile.
In spite of changing settings, re-booting etc I could never get a fix at the time, although it does seem to work at the moment.
I can only think that the combination of poor/unstable broadband and failures in the mobile network were a cause, but I could never prove it.
I suggest you raise a technical query with both BT and your network provider - get their wizards to investigate!
