Impossible to close account

I have a 'Global' forex account that I never use and have been trying to close for months. But FNB won't allow me to close it unless the balance is zero - and somehow it's overdrawn by 20p. That's less than R5. There is no way to get the balance to zero, as my FNB cheque account no longer exists. I've tried funding it with R100 from my Capitec account ( a lot more than I owe) but the money just gets returned. How do I get rid of this account and FNB's demands that I 'Fund it within the next 30 days'? I get sent from department to department and endless emails later., nobody can sort this out.