International Roaming Charges

On July 19th I returned from celebrating my wedding anniversary in Europe. When I arrived in Europe I received a text inviting me to join Global Travel Pass by responding with a Y for yes. I did this as instructed. I assumed it was taken care of. Imagine my shock when I arrived at the airport in the USA and received a text that I had $1,700 on roaming charges when I had done what was required. 
Also, your policy states that you will monitor roaming charges and notify the customer when accumulating roaming charges become excessive. I believe you will agree that $1,700+ in charges is excessive, yet I wasn’t notified. 
In Summary: 

1. I responded to the text regarding Global Tavel Pass and believed it had been activated. 
2. I wasn’t notified that exorbitant roaming charges were accumulating until I returned to the USA. This seems completely unjust. 
I am a retired law enforcement agent and this amount is causing me a lot of stress because I can’t afford it. I want to remain an Xfinity customer as I have been for years, but this episode is alarming to a long term customer. Please assist me by crediting this unjust charge. Thank you!