Harrased, overcharged, FNB unable to fix own system errors and others pay for it.

Last month 24 August they debited my cheque as usual to pay my revolving facility however for some reason I have been harassed with SMS, calls, email that legal action might be taken against me for an up to date account. I sent a post here and my complaint is still in progress and just yesterday FNB went on anyway to debit my account twice for normal monthly payment and the non existed arrears amount. these amounts are both reflected on revolving facily and this morning the calls continue that I have not made payment my account is in arrears and all this time my account has never been in arrears transaction is all there and o help almost a month the issue just keeps piling up.