DangDave

Many users in the U.S. are now keeping their mobile phones longer due to the elimination of the two year subsidies that used to be offered. In the past we could turn in our old iPhone for $250 or so which paid for the $200 upfront cost of the subsidized plan for a new phone. 

Now the main reasons to get a new phone are to get HD voice, wifi-calling, Apple Pay, more storage, and other features.

For the iPhone 7 the "World" phones are models A1660 and A1661, which is also what you will get from Verizon and Sprint. You can pop in a GSM sim from anywhere in the world.

To work on a CDMA network they must be provisioned by the provider. 

The issue is NOT ApplePay. The issue is that Walmart does not want to pay the 2 to 3.5 percent fees that Walmart and any other store has to pay to the banks if they allow bank credit cards to be used.