Telkom High Billing

To telkom. Went to the shop yesterday and had a wonderful person that did her best to help me with my account on why it is so high. After a few discussions to the billing department we got the reason. There was an unauthorized USSD subscription charge. Here comes the best part. SIM card never left the router since I got it and there is also no subscription active. What is the best thing to do as I cannot pay the amount? Still waiting for the billing department to call me back.