No credit app**** for returned item

On the 11 December I bought jewellery online from the galaxy store to the total value on R759, 1 item was canceled because they weren't able to source it and the other of R399 was delivered. I returned the item via courier collection on the 15 Dec. To date I have called 6 times as the R399 was never credited to my account. Each time I am told it will be resolved in 24 hours... Still nothing!! I called again this morning to be told the same thing. Nowmy balance is higher meaning my installment is higher! Even during this tough financial situation our country is experiencing I paid my account on time every month. So why can't use fix my account. This is unacceptable yet you are so quick to list people when they don't pay but you guys can't do your job properly. I need this resolved ASAP