The first thing I’d do is to check network status to see if any work is being done on local masts. Don’t forget you can use WiFi calling on payg or contact whereby you connect your phone to your home internet connection. It’s enabled by default by Three you just need to turn it on in the settings of your handset. I use it myself as I live in quite a rural area and can confirm it works faultlessly.
Hope the info helps you.
