 As long as that cell phone is operable and even if it doesn't have a plan on it, if it can catch a signal, it will work on any of the major wireless carrier signals to dial 911. So in a true emergency, yes, you would be able to dial 911. Even if your phone signal is, you know, if your phone isn't connected, whatever, you know, it's having some sort of issue. Now, if the signals are down, yes, that would be a problem.