I want my money back but Shop refuses

I made a Lay Buy on the 17th of October 2020 at the store here in Oudtshoorn, and yesterday I paid it in full and got it. When I got home I fit the dresses and it was too small because I am currently pregnant. I called the store and told the lady that I have the lay buy slip, but not the slip when I made the lay buy with... due to the move from one place to another. She told me that the store won't give me a refund because I don't have the original slip. I said but I have the lay buy slip that I paid in full... I want my money back. I asked to speak to the manager upon which she said that the manager will say the same thing, so it's no use. I insisted but she refused. So I dropped the call. I don't want anything from ackermans, I want my money. I need the cash for school clothes that's not available at Ackermans.

I want my money back and I want it urgently. Kindly contact me because I am not happy with this service.