I suspect the staff is confused:
Ipads upon their initial release had an unlimited data plan through AT&T. They stopped offering this plan to new purchasers after just a couple of months. They are grandfathered and transferable, so if you purchased an iPad in the first month or so of their release, you could move this to your future iPads. Recently, AT&T began throttling the speeds of this plan if you used "too much". For new purchasers, this is just history, as there is no way you can get your hands on the ancestral unlimited plan.
I abandoned my grandfathered iPad plan last week for an "unlimited" plan from T-mobile, which has much better coverage in my area, higher speeds, and is more "unlimited" than the AT&T version, and provides better for international travel.