Was told I'd receive $25 credit per month on my UVerse bill as long as I had cellular service

Colton Huff - ATT sales person that set up our new service told me - in writing via email - that I'd receive a $25 credit per month on my uverse bill as long as I had cellular service.  He failed to mention that I needed to have unlimited data plus on my cellular plan.  I have emails back and forth before we agreed to our new service confirming all of this.

I have talked to at least 6 different customer service reps and emailed Colton Huff twice as well as left a message with his supervisor.  I feel like I have gotten nothing but the run around from every one of these people and no response from Colton or his supervisor.  I've been told everything from the credit has been applied to there's no way we can give you the credit.

What do I have to do to get ATT to stand behind what I was offered or do I just cancel my service?