Xfinity mobile billing [Edited] up after getting a refund

I initially bought a new Xfinity mobile plan with an iPhone 17 pro since there was a $400 discount. This was on a 2 year monthly payment contract. After a few days I was charged the full amount of the phone accidentally by a customer service person. That’s when the issues started. 

I spoke with billing support for multiple weeks to finally get a $400 refund back. 
This refund seems to have [Edited: "Language"] up the billing system since after getting the refund, the app was showing that I owed $400. I spoke to the support people and they said it looks good on their end and to my surprise account was suspended after a few days. Because the system showed an unpaid amount of $400. 
I keep running into this loop of getting the refund and the system detecting that as an issue and charging me the amount back. 
are there any competent people in Xfinity mobile billing who can help resolve this issue one and for all ?