How I handle data…
I enable wifi on the phone and connect to my home Internet (Spectrum). The phone uses that when I am home and I am not having to use my data that way. It may be an obvious solution to people or perhaps not. If I was to go on a long roadtrip, I can always turn off wifi so the phone is not constantly looking for a signal and using battery.
If you have an old cellphone around the house that has once been on a network and still has a SIM card in it, then it should still be able to call 911 even without a current plan.
Also, old cellphones with wifi capability can still be useful at home for things like TV remote control. I have both TCL and Roku apps that use the wifi in an old phone to control the TV if I have temporarily misplaced the remote.