Mobile Billing long-term issues

We signed up for a new phone promotion with Xfinity on June 20, 2025. As such we had to upgrade to a Premium Unlimited Plan to get a $400 discount per phone on 2 new iPhone 16 Plus phones we purchased. Everything was fine in the store. Subsequently on our monthly bills, some months showed no discount of $16.66 per phone per month. (Xfinity were supposed to pay us back the $400 discount over time) Every time we called they said it was because somehow our account shows that we changed our plans again on June 26, 2025 - which we never did. Because of this they claim we our discount was invalidated. There is no reason we would ever do that just a few days after getting 2 phones and 2 new Premium Unlimited plans. I've spoken with Xfinity many, many times over the past 8 months or so, and each time I get a different answer. Sometimes they can't do anything, and other times they give us a one time only discount for that month, and sometimes they say it's resolved (but it never is). Today Feb. 4, 2026 I did get someone to agree that our issue was valid, so she put a note in our account that we should be getting the discount every month. She was able to get that for our upcoming Feb. 14, 2026 bill, but not for other months. I called back this evening February 4, 2026 again to validate, and they said there is no note in our account, and that they will not honor our discount. In our estimation it's Xfinity's fault, and they are blaming us. It's very obvious we would never do what they said. There is a chance that the in-store people had something to do with it as we visited the store a few times around the time we bought the phones, but again not our fault. Xfinity is blaming us for something they did, and it isn't right. All we want is the plan we signed up for, including the iPhone 16 Plus x 2 we have, the $400 discount per phone, and and the Premium Unlimited Plan which should not be so difficult. We just want what we agreed to.