What if the call gets cut off just because it's a bad line? What if the jammer takes effect 500m before the first vehicle? What if the phone runs out of battery

What if the call gets cut off just because it's a bad line? What if the jammer takes effect 500m before the first vehicle? What if the phone runs out of battery, which it will within hours if it's active on a call? Not to mention that finding the IEDs would be much easier if they were radiating like a mobile phone. All just guesses of course.