no MMS on GCI towers

I am unable to recieve or send MMS messages when connected to GCI towers in Alaska. SMS, call, and data all work fine. The issue appears whenever I am on GCI network, and disappears when I drive through an area with t-mobile coverage.

Here are the details of my issue:

• Google Pixel 6a
• Android 13 build TQ3A.230605.010.A1
• T-mobile prepaid

Error messages:

• Message expired or not available
• Trouble sending

Here is what I have tried:

• various recommended APN configurations
• Ensure my plan and balance are valid
• Restart phone and reset connection with airplane mode
• switch texting apps / clear and reinstall app
• disable wi-fi calling
• update android

while these solutions worked for others, they did not for me. What are the next steps towards finding a solution?