Totalsports Jane furse crossing treating customer as some trash

On Wednesday I went to total sports Jane furse crossing to buy some shoes, I had a credit avail of R880 on my jet account and I paid R1000 to my jet installments. When i was buying those shoes, I asked a cashier to void those shoes and give me another one they denied and said is not possible coz they made some cash up, and told me to come back tomorrow to make exchange ...I went there on Thursday morning since it was my son's graduation and need those shoes for him to celebrate. They treated me like trash, they took those shoes to make exchange and denied me with another shoe,they said the exchange money went back to my jet account and I don't have avail credit money to make a purchase. On Friday I went there as well but the manager treated me as if I stole the shoes, I told her to call their head office but they said their phones are not working, I gave her my phone but she denied. I went to Jet store to seek for help they said the R1000 which i paid is not reflected on my account.