Escalation for Credit of Roaming Charges

Before going on a trip to Canada, I tried to activate the Mexico/Canada travel pass. 
Apparently, it was still in a "pending cancellation" status for four months since my last trip. 
Because of that status, I could not activate through the app. 
I contacted Customer Service (before my trip) that I needed help activating the Mexico/Canada service. 
It seemed like they were having technical difficulty doing it through their system, but I was reassured it would be done. 
I travelled to Canada and within a day of being there, received text notifications that I was incurring roaming charges.
I spent over an hour on the phone with Customer Service explaining the situation. They agent could see all the notes in my file regarding asking to have the service activated. I was assured that I would not be responsible for the roaming charges. 
After that interaction, I received a survey about my experience. I responded that I was unhappy and concerned about the charges. 
I received a phone call from a CS person, who reassured me that the notes were very clear that I had requested the service prior to my trip, and that I would be credited for the roaming charges. I asked that the credit be issued right away, but I was told that the credit could not be given until after my billing cycle had ended. 
I called back after my billing cycle ended and spoke to a CS agent who said that he could see the notes in my file, assured me that I would be credited for the roaming charges ($855) but that he was not authorized to perform the credit himself. He needed a supervisor. I was on hold for an hour, waiting for a supervisor to become available. When she finally came on the line, in very terse terms, she stated that the charges were valid and that she could not credit me. This, after the first agent said it was absolutely clear in the notes what had happened. The second agent was quite rude in saying that there was nothing she could do, that she could not transfer me to anyone else, and basically "tough luck, lady". 
I got another survey about my interaction, to which I gave a scathing reply. 
Then I got a phone call from CS asking me about the survey and my response. I explained the situation again. 
She looked in my file and could see all the notes. She said she had to speak with someone else about it and call me back. 
I have not been called back yet. 
How can I get in tough with someone who can actually help me, in real time, to get this resolved.