Fnb private banker

I have been complaining with my black card that i once use it.. i tried to close it but the told me i need to pay up my negatives which was 1000 something i didn't have any problem with that my problem its is... how can my negative keep increasing to 9 000 and i never get any call or latter from my my private banker .. can you please help me to close this account.. and am a fnb customer