Interest charges more than acrual debt

Had an fnb overdraft in 2022 was furnished with a clearance certificate by my debt counsellor included was this over draft. I assumed all was good even got a credit card by capitec. 2 months later found out my clearance certificate was rejected by fnb, in 2022 the debt was R69 000, now is R148 000. I called their debt review department was informed account is with our legal department, call them was informed that they do not have the account this back and forth has been going on for weeks without proper answers but yet charged monthly interest of more than R3000 the interest amount is double the actual debt. Now how is that ethical and legal, i can't even explain my distaste for this institution I don't get any positive feedback. I will never bank with fnb again.