There error that I must pay

Very disgusted in the service received. The agent I chatted with has so much attitude. I got a free R50 play for my bday which they loaded incorrectly to mynormal account and not bonus account I then played it out and they put my account in a minus and expect me to pay it back. So who's fault was this mine or Theresa's I was not aware of how it works and that it was for specific games and it allowed me to play it. Now my account is in a minus nd they expect e to pay for their system error. Bull**** I want this fixed. Contact number ***. The agent was not even willing to escalate this as he said he explained the error and this doesn't need assistance.