Yes whichever number you used to buy the 12 Pro Max will be the number you use on the trade in offer. The IMEI is just for AT&T to determine what phone you have and if its paid off/reported to insurance.One of the questions on the ATT trade in questionaire is to provide the phone number and IMEI/Serial of the trade in device. I currently own a XS Max and will upgrade to Pro Max using the $800 credit. I also plan to purchase a used unlocked iphone 8 on ebay which will be used as the trade in. Then I sell the XS Max on Facebook marketplace. I assume I use the line # on my XS Max (soon to be ProMax) when completing the question on phone number even though that iphone 8 was never used on that line?
[automerge]1602954516[/automerge]
Trade in page. here: https://tradein.att.com/offer-detailsWhere is the fine print or terms. On the trade in page or when enroll.