I have a housemate using Sprint in the USA that periodically gets totally bogus charges for alleged international calls that were never made. When he calls customer service the one drawing the short straw gets him.
I’ve never had a wrong charge on AT&T......however, I don’t make any overseas calls, either. My point about the lady paying the charges is that sophistication and technology pays a price. Those who use it blindly can end up surprised. It’s just like ignorance of the law, it’s no excuse for not even wondering (which I think she did because she’d cautioned her daughter and ‘agreed’ on usage) She just didn’t follow through.