Incorrectly labelled item

I went and bought some new swimming briefs yesterday 7 September 2017 and the size on the hanger said 32", I get home after the gym and realize they are actually a 30" and were incorrectly labelled. It was not my fault that the hanger was incorrectly labelled.. I have already taken the label off now though.

Paying R500 for something that I now cannot use due to a merchandising issue because of the fault of the store staff is really unfair. Please assist me.