When Moze is left with only 3 minutes of cell phone time she says she can't answer Faymen's call because there will be none left. This isn't true. Minutes only run out when you make a call or text someone not if you take one.
When cell phone calls are ended, the non-hanging-up phone goes to on-hook mode. It will not make a dial tone. Dial tones aren't even applicable to cell phone usage. (In the US, residential land-line phones will generate dial tones if the other party hangs up, since the phone being off-hook literally is off-hook and creating an open call circuit with the central office.)