Erroneous billing for promotional cellular line

Hello!

I started cellular service with xfinity last November using home internet promotion, which covers the $40 monthly charge of the unlimited line. Last month I began to notice a recurring charge on my cellular account, at $42.44 monthly. Billing break down indicate that the $40 promotion credit is not applied and I was charged full monthly cost. Reached out to xfinity online chat agent on Jan 27. Agent promised to refund previous erroneous charge in the form of home internet account credit, and rectify future cellular account billing. However, as of today, neither of the remedies took place. I am reaching out to online community in the hope that staffs here is more helpful... 

The ticket number for this issue is: ECM0019383441.