First- and second-generation Kindles did not come with wi-fi functions included, using mobile internet only.
But the slower technology used at the time - 2G and 3G internet - is being discontinued in some places, particularly the United States.
Several other models will also be restricted to wi-fi only.
The mobile-capable versions have historically been more expensive than the equivalent wi-fi-only models.
But aside from that upfront cost, there is no mobile-data bill for Kindles - Amazon pays those fees to keep customers connected to its online store.