In Duplum Rule violation

I have made numerous attempts to get feedback from FNB but to no avail. I am under debt review an overdraft of R5000.00 as no incurred interest, penalties and charges amounting to R24000.00 this is almost 5 times the initial value.

According to common law practices in duplum interest, penalties and additional charges can only go upto double this amount.

I do not know how else to contact FNB. Please see extract below sent to the debt review department: i downloaded this from a fin24 publication.

You are further protected by the In Duplum Rule which stipulates that the fees and interest charged may not exceed the outstanding balance as at date of default. If the outstanding balance was R20 000 as at date of default, the fees and interest charged may not exceed R20 000. Should this happen the fees and interest may no longer be debited against the account.

My current account has moved from a debit balance of R5000.00 to R29000.00

This is almost 6 times the original value. What type of recourse do l have in this situation?