Wrongful Charges due to Xfinity Mobile Mistake

Since Apr 2022, I have paid $917 on charges due to a mistake that Xfinity Mobile made where one of my lines was moved to a separate account that I did not have access to but that still billed my credit card each month. After trying to fix this issue over the phone and in person over the course of months, the root cause was finally fixed Sep 2023. Now I am being told that the policy won’t allow this refund to take place. Several agents I have spoken to would like to help but they cannot because it is not within the company policy. After 18 months of frustration I am hoping this will be my last attempt to resolve this matter before seeking legal advice.