IT seems like its of his best interest to just fucking call verizon and be like “Bitch who is this”
and see what they say. Of course they do not have to (or legally cannot) give out that kind of info to someone.
Hell if someone put a charge on my bill I would get the cops involved. CC fraud or what ever fraud will get things moving… Then you find out it was your mother that you said it was ok to do something like that