Today Verizon has announced that it's going to have basically the same deal up for grabs starting on Monday, January 29, "for a limited time". You get $699 off a second iPhone 8, 8 Plus, or X. In order to be eligible, you will need to purchase both devices on device payment, activate a new line on Verizon's unlimited plan, and trade in an old phone within 30 days.
The $699 discount will be provided as a bill credit to cover the cost of the device over 24 months. The offer is available both for upgraders and switchers. When you trade-in your old phone, you will receive the trade-in value of up to $300 in addition to the bill credits.
T Mobile never had the deal on iPhone X, as much I know.
The T-Mo deal is better..You get $700 in terms of a gift card, not credits like the VZW deal doeth....