Auto Payment Declined for unknown reasons and was charged with Past Due. Unable to reach customer care

Hi,

My xfinity account has a problem with billing. I have been xfinity Internet customer for almost 3 years now(with mobile services active for an year too). I have been doing autopay with same Master card ending with 6186 and the last payment was made on Jan 15. The Payment was declined on Feb 15 for unknown reasons and I was charged with Past due balance. I did call customer service on 02/26 and the agent I was in call with (Marie), have assured me that there was some system issue and she took consent to process the payment and she said payment was processed and I will get confirmation in 24-48 hours. She even mentioned the $10 past due fee was waived as well.

I have been checking my account from then and seeing no payment update was made and still showing as Past due. I am concerned and disappointed as customer. 

1. My Credit card is actively being used and no reason for it to be declined. I am also using 3 mobile lines with xfinity and the same card successfully worked for auto pay to pay mobile bill. Issue is with core services bill.
2. Agent communicated very clearly that there was some issue and she corrected by applying payment, which was never reflected till now. Trying to connect to xfinity agent is a nightmare.
3. I am trying to change services now for a lower speed tier, and was being asked to made a deposit, even though I never missed a payment till now for last 3 years and the process has been tiresome.

Pretty Disappointed as customer and would greatly appreciate if someone resolves this quickly.