Purchase paid but not received.

Today at 11:53 I visited Ackermans at Jubilee Mall , Hammanskraal in Pretoria and I was assisted by a cashier by the name of Kearabetswe Mwale. I bought a Vodacom data for R49,00 using my Ackerman's account,she gave me only one receipt and gave me one to sign then took the signed one which I thought she gave me the receipt with the data PIN but she didn't and I realized it when I was just outside the mall resting when I wanted to inset the data onto my phone I realized that there was no PIN receipt. I went back to Ackermans and explained the complaint to them that I was not given the Data receipt and they said they will fix it and I believed them since I showed them the receipt their cashier gave me. Then they called another cashier to assist me and not the one who helped me previously, now the second cashier asked me for my account card and did another transaction instead of giving me the data that was not given to me the first time and also inserted it into my phone therefore I believed that they gave me the first data transaction but when I got home and checked my receipt I saw that they had made another purchase instead of giving me my first purchase and now I paid for something I didn't receive and they expect me to pay the account in full at the end of the month. I don't understand why they **** to me saying they gave me my first purchase when they didn't yet they debited my account twice. Please can some one advise.