Hi, welcome to Just Answer.
This truck has a defective Ignition Lock Cylinder, they will remove it and either have the tumblers repaired or an entire new cylinder installed, definitly should be under warranty unless somehow you physically damaged it, like sticking the incorrect key in there.
Hmmm, it wouldn't make any sense unless they are refering to the Ignition Switch, which is right behind the Ignition Lock Cylinder. Could you possible ask them the area this part is installed? If it's in the steering column, than it is the Lock/Switch.