Promised Promo Credits not received from Dec 2024

I had brought two phones Samsung Flip 6 and iPhone 16 Pro Max in Dec 2024. While buying these phone there were two promotions. a) $400 off or 2) Trade in. The customer associate at the Tracy, CA store helped me to understand the difference between these two and suggested me to take the trade in, as I  can later decide to trade in or not, if not traded in it shall automatically apply the $400 promotion. I took this option as I was not sure at the store to trade in or take the device promotion.

Later when, I decided to keep those trade in phones as the backup phone, I decided not to trade in and waited for other device promotion to kick in. However, I as unsure about this, I did call to the customer care back in Jan and told him to cancel my trade in, for which he said he has to send the request to backend. Today I see that I do get the trade in for my Flip 6, but not to the iPhone 16 Pro Max. Every fifteen days I reach to the customer care for the update, and I have been told that I cannot get any credit now on iPhone 16 Pro Max. And aslo I quote my other example where I do get the credit for Flip 6, there is no response. 

Please help me to escalate this, and get me the promised device promotion on my iPhone 16 Pro Max.

Offer number [Edited: "Personal Information"]