Unacceptable - begging for paid up letters, now interest accruing

I've settled my account in July and asked FNB several times to send me all my paid up letters, to date (Oct), I haven't received it. Now, the one account is accruing interest on a monthly basis since July. The inconvenience is unspeakable. The customer service lines are appalling and no one is available to assist. The FSCA should look into this complaint, because this conduct is unacceptable.