Impossible to resolve issue with Xfinity Mobile Customer Service

I'm trying to address an issue for my 94 year old mother (I'm on her account) and am running into nothing but obstacles.  After my parents house burned down on December 30th, 2021 (part of the Colorado Marshall Fire disaster), we relocated my parents through several temporary homes and ultimately set up Xfinity Mobile accounts for both parents (ages 92 and 96 at the time).  Unfortunately, Xfinity Mobile did not allow use of a flip phone and so they ended up getting two Motorola smart phones on Sept 23, 2022.  I was put on the account as an authorized user because neither parent texted but xfinity billed my Mother's credit card.  My father (97 at time of death) then died on 10/29/2022.  I provided a certificate of death to Xfinity soon thereafter and returned his Motorola phone to xfinity locally.  My mother suffered a broken hip, post-op stroke and numerous other medical issues which rendered her even less capable of using a minimally configurable smart phone so on March 16th of 2024, we cancelled the phone line(s) officially (with confirmation from Xfinity) and got her a flip phone with another carrier.  Xfinity continues to bill her Mastercard and seemingly has no one with the desire/capability to deal with this issue.  It's borderline criminal for xfinity to continue to exploit this situation.  I've had no luck with voice and can no longer sign in to the xfinity website to deal with this directly.  Please don't tell me to log in and send a private email unless you also provide some link that works when the account has been disabled. FYI, because of this, I cancelled ALL xfinity services including internet on my end - left my mother's intact though as she can't handle any more disruption.  Any ideas on how I can reach someone with authority to review this situation?