How do I get credit for a buy one get one free deal?

Back in August 2016 we pre ordered 2 Samsung Galaxy phones with the buy one get one free. However, Samsung recalled these phones due to batteries blowing up. We exchanged the phones for 2 different Samsung phones. I was told at that time that I would still be eligible for the buy one get one free promotion ( not my fault the phones were recalled). I have been trying since last year to get my credit and every time I chat with an agent I get the same answer, " the credit will be on your next bill" yea right. I have all the transcripts and I just want what is due me. I also received a "case number" for my claim and was told that AT&T needs to investigate if I am even eligible for this credit. Well, I am eligible, I want my credit or I will go further with my complaint. 

Thanks