overcharged

Good Day on 29 of March 2024 I was gifted with a jacket from a friend bought from Ackermans Liberty Promenade she also gave me the receipt as she wasnt sure if I would like the gift so I could exchange it if needed, so Saturday 29 June 2024 while doing my shopping I went into Ackermans Town Centre saw a jacket I liked and asked if I could exchange it here without having a receipt they said Yes as long as the tag is standing in a long line to exchange only to get to the cashier and then she says I must pay a R100 difference cause I paid Marked down price on the jacket I explained to No it is'nt she then continued saying that is what showing on the system so I pay it, then today being 2 July 2024 my husband gets the receipt and i ask him to go and query it cause i should then be refunded management says No they cant refund me cause they had to charge system price and i did not have the receipt so now im a loser of a R100..