Xfinity mobile charged me $908 data roaming fee!!!

Xfinity mobile charged me a $908 data roaming fee!!! I chatted with them on line, called them via phone many many times, explained again and again that this was because my daughter who is a minor BTW, accidentally enabled the data roaming while we ere traveling abroad, the option popped it up automatically and she clicked it without knowing what does the data roaming mean and how much the cost would be.  One of the agent I talked too around two weeks back, waived the additional cost and when I called them today to follow up, they told me that the charge was valid and not waived, I am really lost. The charge is so high ($908 for around 2g) and wondering why xfinity don't automatically apply for the international travel pass in that case?