Unexplained exchange policies.

I am very disappointed and completely appaled by their process.

I baught a pair of shoes/boots for R169. 90 and it didn't fit I wanted to exchange it but they said I can only exchange it for R60 due to that particular shoes being on special. My question was what happens with my R109.90 that I will loose.

Now I'm siting with big shoes and unable to exchange it.