Xfinity is charging more than our agreed base rate and won't make it right!

In August of 2022, our beloved internet rate of $49.99/mo was due for an increase. We chatted with Xfinity to negotiate a new rate and were told that our new base rate was to be $75/mo but we would receive a $20 monthly credit to offset the cost of the base rate. This would bring us to $55/mo out of our pocket. We confirmed over and over that this was a recurring credit of $20 PER MONTH for the duration of the plan (24 months, $480 total credits over the course of 2 years). We agreed to $75/mo plus $20 credit = $55/mo. 

However, Xfinity is not honoring this agreement even though we have reached out several times since August to confirm our deal. Each time, they *fake* confirm our deal and assure us we will see the appropriate change on the next bill but nothing has been honored yet. 

Here is a breakdown of our hours and hours of battling with Xfinity:

August 2022 - $20 credit posted after agreeing to $75/mo plus $20 credit = $55/mo. Great.

September 2022 - CREDIT NOT POSTED. Contacted Xfinity via chat and confirmed we should see the $20 credit. NEVER POSTED. (Xfinity owes us $20).

October 2022 - CREDIT NOT POSTED. Contacted Xfinity via chat again and confirmed we should see the $20 credit. NEVER POSTED. (Xfinity owes us $40 now).

November 2022 - CREDIT NOT POSTED. NEVER POSTED. (Xfinity owes us $60 now).

December 2022 - CREDIT NOT POSTED. NEVER POSTED. (Xfinity owes us $80 now).

January 2023 - CREDIT NOT POSTED. Contacted Xfinity via phone. Was transferred to 5 different agents over the course of 3 HOURS and confirmed we are owed all of the $20 credits from the previous months ($100 total at this point). Was told we would see the backlog of $100 credits on the February bill AND receive $20 monthly in credits as originally agreed upon moving forward for the duration of the plan (24 months). (Xfinity owes us $100 now).

February 2023 - NO CREDITS anywhere to be found. (Xfinity owes us $120 and counting now).

At this point, I am at a complete loss for how to get Xfinity to honor our agreement. Anyone have any luck with this kind of dispute? I'm not sure how it is legal for Xfinity to charge us more than our agreed upon amount. We did NOT under any circumstances agree to $75/mo. We have done more than enough checking and double checking that our agreement is $75/mo plus the $20 credit. That is not up for debate.