Upgrading iPhones

I was given a 50% promo code to upgrade my iPhone 13 to an iPhone 15.  My wife and I both have eligible phones to upgrade and we are on the same account.  The system would not allow more that one phone in the cart at a time.  I called Customer Service and spoke to a live agent who explained that once the first phone was activated another promo code would be sent for the second phone upgrade. The first phone was ordered and activated and now the Rewards Program will not issue another code.  Each code can only be used once which was not made clear when I spoke to a live agent before the first phone was upgraded.  After several phone calls and two trips to the Xfinity store they still refused to issue another code.  Three tickets have been generated by agents who say the second phone is eligible and quickly closed with no explanation.  They just say the issue has been resolved which it has not since another code has not been issued.  I even had an agent tell me they reinstated the original code which they have not. I feel that they enticed us with the offer, answered our questions incorrectly and basically gave us misinformation.  Who can help me get my new code?