Refusal to Provide Billing Credit Agreed to in Writing

I signed up for Xfi Complete and due what I was told was a system problem I never received my home evaluation results or coupon to purchase Xfi Pods. After a few chats with support on August 9 I was offered a statement credit of $199 if I purchased the Xfi Pods. I was told that I could buy them and after I made the purchase the $199 would be automatically credited to my account (again this is in writing - I have the screenshots from the conversation). Since then I have contacted support through numerous chats, spoke with a billing agent on the phone, and had 2 support tickets opened to have the credit applied, both of which were denied. Each time I am not provided the rationale and the agent I chat with confirms they can see the chat transcript and that I was offered a statement credit and they are sure the credit will be applied. 

I am not sure how else to proceed here. I am happy to provide the screenshots to support but this is also visible information to Xfinity support. I am not sure if there was some reason the agent should not have offered me this credit, but she did and I accepted. I cannot figure out how to get any further with support that keeps opening tickets that get denied a day later. If anyone from support could DM me to review this information with me I would greatly appreciate it.