Please help me to get an exchane or my refund of R550

i bought an airbed on special last year and kept it in my garage, unfortunately last weekend we decided to go out camping.. to my surprise after pumping the beds in the following morning we all woke up on the ground ,which means they were leaking out air i then decided to go the by the department today sartuday 30 March since the whole week i was busy with work and now they denied my exchange and they said my warrant expired 2 days back..! the funny part is i call to my request telling them i will come on saturday and they said it was ok ,