Been disrespected and bad service

On the 24th July i went to Springs Mall vodacom to buy car charger and a cable, just to realized later same day that cable was wrong, today 12 August i took back the cable best for exchange to the correct one and honestly i don't remember what happened to the slip, i drove there with the hope that they know their brand, they will help me peacefully but i was treated very very bad in the extended of lady who was assisted took old used cable from her handbag, to replace my brand new one, though mine wasn't used at all, either to be refunded my cash back they refused, i was angry i even left the cable with them cause i felt that they is no use to keep something that i can't use. I had date, time and a card that I used on the day, i believe those things should had assisted them but nope.