Denied my right to an exchange

I bought boots at Mall of Africa day before yesterday, when I got home I discovered that one shoe is a size 4 and the other a size 7, obviously 1 has a price tag on it. The shoes were not paired, each was separate.

I went to Pick n Pay Maponya Mall for an exchange, and the lady at customer care told me that she can't accept the shoes, it will mess up her stock, now who has to buy that size 7 and 4. I asked if it's my fault I bought a size 7 and 4, is it my fault the shoes were not paired. Didn't I buy from the same shop, what do I have to do with the shoes now?

She told me to go and exchange it at Pick n Pay Mall of Africa, mind you I took a taxi to Maponya Mall and it is the closest, now I have to spend another R100 take a taxi to Mall of Africa for an exchange, when will I even get the chance to do that.

I called customer care, and the lady agreed with Maponya Mall, she merely opened a case of unmatched shoes. That is not enough, I was denied my right to an exchange, I'm very upset about this, I spent my money on these shoes, what if I wanted to wear the shoes yesterday. Pick n Pay does not care about me as a customer. I'm very dissapointed.