Ongoing harrassment! Close my account with immediate effect

I have had enough of this bank. I am disgusted by two debt collectors who have been contacting me after my account has been paid and settled, with a settlement letter. In what world does FNB send debt collectors after you after you have paid and the account has better settled. Damn right harrassment and as far as I am concerned this is *******. Sort out your bank quick and resolve me account with immediate effect. I have rights to take this further and trust me I will!