1. I received my iPhone 16 Pro Max on 9/20/24.
2. I canceled my first trade-in for the 14PM on 9/23, which I pledged on 9/13 online.
3. I set up my second trade-in attempt with the iPhone 12 via tradein.att.com on 9/27.
4. I canceled this second trade-in on 9/28, helped by my local AT&T store, because the trade-in was logged as a plain trade-in without 36-month credit.
5. Finally, I successfully completed my third trade-in attempt with the same iPhone 12 at a local AT&T store on 9/28.
AT&T doesn't double-credit on any number. I had already paid off my previous iPhone 13 Pro Max two months in advance, which means I won’t be receiving credit for those two months from the previous promotion. However, I successfully secured a credit-backed order for the 16PM this time around.
To clarify, you can place a new iPhone order with the 36-month credit applied only after paying off any prior promotion for the earlier device on the same number.