Paid account but TFG says they can't locate payment

I paid my Foshini account on the 14th of May at Jet. A few days later I started receiving calls that I have not paid my account. I tried to explain numerous times but I was told to go back to Jet to locate the payment of R400. Jet then told me they can't assist me, I must go get a bank statement! All this even though I have my store receipt as proof. I called collections as they threatened to blacklist me. I then told to email my receipt to the electronic payments team. I did this twice, but issue still not resolved. I even sent it to the supervisor at collections. I had to pay R500 on 15th of June because the matter was not resolved. I have called customer service but no one seems to be able to help me. I have pd R900 in the past two months but only have R242 credit because they charged me for all the phone calls and emails even though I did pay. I even sent a bank statement but still no response. This is terrible. How do you lose your customers payments?