Mobile Billing Not Honoring Promotion

I signed up for Xfinity and switched over due to a promotion that offered 1 year free line with Internet subscription. Ironically this promotion is still ongoing and being advertised. For the past 2 billing cycles I am not getting the $40 credit and again this month cycle there is no credit applied again. I have chatted and called multiple times and speak to offshore reps that argue with me about it. I have been told they will give me half the credit as a courtesy or telling me its a 1 time courtesy. Ultimately I get the full credit but I shouldn't have to fight for it every month. I have asked for Managers or an escalations department and I am told that its not available. I have spoke to the Internet side and they see the promotion and they say it was loaded and entered correctly. They have no clue why my mobile bill isn't reflecting the promotional credit. 

This is exhausting and not respectful of my time. The internet side has told me that they cannot help me as the Mobile side is a different area. Who can I contact to help me? Im honestly about ready to just go back to AT&T and T-Mobile.