Just Kept charging

A while ago (so long ago, I can not tell you the date) I had canceled my FNB account. I subsequently moved on to another bank and this week received a mail from FNB. It seems that they did not close my bank account and now want to claim that I have to pay them the R185 that accumulated each month. This ended up several thousand rands worth of fees. For a service, I had canceled? This is nothing more than FNB trying to ***** from me. I dispute this debt wholeheartedly and will not cave in to pay money to a bank just because they could not follow instructions. How on earth!!!! There has been no movement on the account at all for well over a year, probably even 2