What I do is that I turn on WiFi calling in my Android device. Works kind of OK for the most time. Another solution would be Fento Cells, which provide small BT

What I do is that I turn on WiFi calling in my Android device. Works kind of OK for the most time. Another solution would be Fento Cells, which provide small BTS, getting the upstream connection via your internet. Yes, you pay for your phone and for your internet bills, but, in such places you are happy if this provides you with phone connection. I didn't find this mentioned in the article.