"In Warehouse or Direct Delivery Only. Buy an iPhone 8, 8 Plus, or X on an Equipment Installment Plan (EIP) and receive $700 over 24 or 30 months, via monthly bill credits. Requires at least one new line of service.
Looks like you could do it directly from an ATT store as well:
Pretty decent deal if you're okay with losing a number and need 2 phones.