Harrassment by TFG due to their internal error

On the 30th December 2019 I called TFG customer service to ask why my debit order has not gone through as my debit date is normally the 25th of each month. The lady I spoke to told me the due date for collections is the 15th of each month and it should have gone through. She went on to check on my account profile and told me that I had overpaid and there is no installment for December 2019. She then confirmed the amount that I overpaid to be R1150.00. In January 2020 all of a sudden I am receiving calls requesting me to urgently make overdue payment on my account. I then asked since when do I owe anything on the account when I made the courtesy to call and ask why funds were not deducted from my bank account in so many days and was told I do not owe anything on the account.

I received another call again in January 2020 asking about the overdue payment on my account. I stated clearly that I would under no circumstances pay funds I no longer have when I called the store to ask why they have not deducted and they told me I am not required to make any payment. The lady sounded as though she understood where I came from and I told her the balance would only be paid in 25 January 2020 together with my January installment as I no longer had enough funds on my bank balance to make this payment. I expressed how I felt I was being harrassed as if I am a non paying customer when the problem is on the store's side. I have now noticed that my account is blocked and there has been charges added on to my account for calls made to me together with interest all totaling to an amount of R157,20. Under no circumstances will I be treated in this manner and end up paying for these charges. The store should take full responsibility for the error. As you would also state that your calls are being recorded, I suggest that you check the record of the 30th December 2019 and deal with this issue internally before harrassing me for non payment. I have had this account for more than 2 years and have never missed a debit order, with one error that has happened internally in the store I am now under harrasment. I will not make payment until these charges have been removed on my account. Alternatively, please inform me if this is how I will be treated and should consider leaving this account.