I am sorry BUT I cannot understand this need for instant communication, we got by very well with the red telephone boxes in days of yore should you need one. It is nice to have instant communication but there still many black spots where you cannot get a signal anyway. What did we do 20/30 years ago when mobiles were darn big boxes and no signal, and even now there are many places where you cannot get a signal so it is back to the red boxes. So what is the problem of waiting till you get home/office and making a call from there.
I was out dog walking out in the country with the dogs and had a mobile with me, I had a minor hart attack and tried with the mobile to get help but couldn’t get a signal and crawled back to the car with the dogs and had to drive to the doctors who called a ambulance and taken to hospital and spent 3 days there. If you have a piece of equipment like a mobile telephone it should be able to pick up a signal where ever it is otherwise it is a unreliable expensive piece of kit and not worth the money.