First National Bank
Incorrect Min Payments calculated

Each month FNB calculates the wrong min payments on my CC, which results in my account going in arrears.
When the min payments are calculated, shouldn't the min payment calculation be done to prevent the straight facility going in arrears?!?
The call centre agent did not get this, she kept on telling me the same story, "there must be enough funds in the straight facility", which again refers to my argument above, especially if I very seldom use my straight facility...