I am in a situation, where I have to switch technologies:
Vodafone is switching off the SureSignal technology in December. I have been using one of these for many years in the house to give us cell connectivity, which otherwise I would not have at our place in remote Marlborough. Our Internet is with a wireless network (not cell network) provider.

I realize I can use various apps on the phone(s) for other people to ring me like WhatsApp, skype etc. , but it depends on them using the right apps and requires multiple attempts depending on whether I am currently connected to a cell network or wireless at home, right? I am looking for some guidance in terms of what technology to use.

I also have a Grandstream HT503 and a Pi and was planning to join landline and a softphone app on the cell phones and computers (see point 3 below), but this SureSignal drama needs to be sorted first.

Here is what I would like to do:

1) Ideally keep our existing cell phone numbers
2) incoming calls/txt using this numbers will be routed to our phones - I guess this leads to WiFi Calling
3) bonus points for tying in our landline into the system, so no matter which number is called, both fixed and cell phones ring

The problem with WiFiCalling is that none of our Android phones is currently capable, so I can not easily check. What is the chance of rooting a spare one I have to get at least one enabled? From my currently still limited knowledge, WiFiCalling should be possible with any phone as long as the right software (modules) in Android are running? Aka it is not really a hardware issue?!?

The alternative is to get a Yagi and mount that further up the hill to improve the cell signal around the house. Trenching 80-100m coax is no mean feat either....

Too many options? Anyone willing to push me in the right direction?