To which device are you referring?

The Fairphone 6+ is compatible with AT&T and T-Mobile in the US and their MVNOs.

https://us.fairphone.com/carrier-compatibility

Oh this is weird. They have some contradicting information.

https://us.fairphone.com/the-fairphone-gen-6-plus

Click on “see all tech specs” and under “compatibility” it says AT&T and Verizon.

But it lacks Verizon’s primary band and clearly can’t be used with it.