Well she would wouldn't she. It could be traced. But even if she didn't since texts are not guarantied, It isn't obligatory anyway. You are responsibly for running up your own bill not expect the seller to act as Big Brother for you.
"Mrs Snook, a catering assistant, said: ‘I wouldn't understand what a data cap was and I don't think a lot of teenagers would." Sums it up I think. I'm trying to find sympathy, really, it is a large bill, but it looks as if some folk are too challenged to be allowed to use a phone.