Unacceptable Customer service

I went to a jet store at the Pavilion for a size exchange for a pair of shoes I bought at Jet watercrest yesterday, when I got to the till I realised I left the slip in my other bag the lady assisting me(Nosihle) told she cant assist me since I don't have the slip and gave me no valid reason, puzzling cause I've done an exchange before without the slip hassle free, I went on to explain to her that I used my store card can she track the transaction, that when she sighed and said she doesn't know the store number of the store I bought the shoes from and left me standing at the till for over 20min, does checking for a store number take that long?I'm heavily pregnant and started feeling back pain from standing that when I asked one of the tellers to please give me my card and I left the store without being assisted