Bank Charges

I have not being using my Fnb account since January.This is due to weird transactions going through my account.I went to a branch and was told that I must pay the charges to close the account.This is unfair as this is now on 3000!I don't mind the 900 that I was aware of.I want the account downgraded to the pay as you use option so that I can continue my relationship with the bank?How does fees go up by 1000 a month.