Credit card payments at Standard Bank

My mother defaulted on payments of her credit card that she has with Standard Bank last year 2018. But since January 2019 to date we have been paying the credit card card every month. We went to the bank in January 2019 to advise them we will be paying the credit card they gave us an account which we have been ensuring that for the past 7 months its been paid. But my mother keeps on getting a phone call from MDB INC that she is not paying her credit card. This has affected her credit score and the bank is saying she must speak to the collecters and the collecters are saying they are not aware of payments