T-Mobile requires you to mail it in. They won’t take it in the store. The key is to get a receipt from the post office to show you shipped it. I got the full amount I was promised, and it was received on their end with no hassle.I ordered two iPhone 14 pro/pro max direct with apple.com
1. Phone 1 was full price iPhone pro max 14 128gb. (I traded in direct to apple retail store my iPhone 13 Pro Max 128gb for $720 plus sales taxes ($50). So they will refund my Amex $770
2. Phone 2 was iPhone 14 pro 128gb on att installment . Trade with att promo ($800 trade in credit over 36 months). I didn’t go to Apple Store to trade in 3 year old iPhone 11. I went direct to att corporate retail store. Att handled the trade in store. They circled $160 trade in value with $800 trade in promo circled printed it out and sent me out the door
I do not trust mailing in anything. If possible do it in the store.