PNA Stationers Castle Gate Warrantee problem.

I bought a LONGBOARD school bag from PNA Castle gate because the staff informed that the wheels and handle have a Warrantee for a period of 1 year. The handle and wheels failed within the warrantee period, and PNA had it repaired, but when I wanted to collect the bag, I was given a bill of R500. The staff explained to me that the warrantee comes with a charge, which is not the definition of a warrantee. I already confirmed with another supplier of the same product that there should be no charge for the handle and wheels within the warrantee period.