Disappointed

I bought a cellphone april 2018 at edgars Cavendish square Claremont. I didn't even had the phone a month and it was rebooting all the time took it back. But i paid the phone finish before i took it back. They send me a message to let me knw i was credited for the fone. So i went today nd told them I dnt want another fone. As i explained to the staff at the cellphone counter dat i paid the fone finish nd my account is all paid up so if they credit the fone on my account my account will b in a minus of R2000. So they telling me that they wont b able to refund me my money. I have my edgars account for almost 18 years nd my account was not once in arrears. Edgars services are very bad as a loyal customer i feel like closing my account with them. Im so disappointed in their service at that store. If i dnt get my money back im gona put them in the papers aswell cos thats my money which they dnt wana give back