Looks like this is a much better deal than having to wait for 24 month bill credits...
confirmation - https://support.t-mobile.com/docs/DOC-32234
1. Buy iPhone 7/7 Plus from T-Mobile at Costco (new/existing customers) - available Sep 16
Must be purchased with EIP/finance plan.
2. Trade in any iPhone 6 or newer model to a T-Mobile store and get $165 or more applied toward the EIP depending on model.
3. Submit rebate application within 30 days at https://promotions.t-mobile.com
using promo code 16SeptiPhone7
4. Remaining balance between phone price and trade-in value (for example, 650-165=485 for an iPhone 6) will be paid as a prepaid MasterCard within 8 weeks of submission.
5. Don't drop your new iPhone in the toilet (or do, since it's now waterproof!
edit: adding terms
- valid 9/23-9/25
- must be on T-Mobile One plan
- rebate may be billed back to account if service is canceled within 3 months.