Was charged extra to return online items in store!

Very disappointed with Mr Price Home in Brooklyn. I returned some unsatisfactory items I bought online and was unknowingly charged a "docket discount" which I only saw on my receipt when I got home (I also bought some other items in store so did not realise the additional cost then). I was not explained to or told about this by the cashier and it seemed as though the return / refund was in accordance.

I queried this on their WhatsApp online chat service (just to understand why I was being charged and what a "docket discount" is) and was told that I need to go to the store and sort it out. It's a small amount and not worth my time but the cashiers and staff need to be aware and explain to their customers what is going on and declare any additional charges.