Lousy dealers say this to dissuade customer from coming to them
for warranty work, which is not well compensated. If they find a
real problem with the car, like it sounds they will, they cannot
charge you. They can and likely will charge you if the service
department just needs to show you how to correctly use your car.
If you bought your car their, I'd contact your salesman or a sales
manager. If they don't help you, I wouldn't even consider buying
from this dealership again. I'd certainly resolve this before your
warranty expires. If they charge you before another dealer's
service department acknowledges or fixes the problem, writing a
letter to the charging dealership and to Toyota should lead to a
refund. P.S. Check that no food or debris has jammed the control
buttons. If that is the cause you would owe them.