Here’s a quick tip.
In the event of an emergency, dialing 911 on any phone should work for free, regardless of whether the phone is activated.
What that means is if you go down to your basement and take an old deactivated cell phone, so long it has a charge, you should be able to make a free call in the event of an emergency to 911. The same is true for pay phones. You shouldn’t need to put money into a pay phone for a 911 call.
Please don’t test this unless you are having a real emergency, and if you do, I didn’t tell you to try it.