HERE’S A SCARY scenario: You’re driving alone in a remote area. Your car dies. And you can’t get a cellular signal.

Don’t count out that phone just yet. Just because your particular service provider—say, AT&T, Verizon or T-Mobile—has no cell towers in the area doesn’t mean you can’t call for help.

“When you make a 911 call, your phone sends a signal to the nearest cell tower, regardless of your service provider,” says AAA Senior Automotive Manager David Bennett. The Federal Communications Commission requires all cellular providers to accept all 911 calls, no matter the caller’s phone plan.

This also works with no service plan at all: An old, deactivated phone can still call 911, but be aware that those phones won’t give emergency call centers your location automatically.—Selene Yeager