DATA ROAMING CHARGES of $522!!

I was traveling this summer and had GTP on the entire time.  At one point I received a message on the airplane that I was using GTP for $10 a day.  Then when I landed in the USA I discovered that I was charged $522 because my phone inadvertently connected to the airplane service (I did not opt in at all).

I have spent countless hours on the phone with Xfinity and even stopped in the store - does anyone know how I can dispute this or get some help?  This is an insane charge for me to pay and I have to think of switching services if I am forced to pay it.