FNB mismanaging my business bank account

I have a business account with FNB , my account was dormant and as a result it was closed and i had to reactivate it. the at bank city assisted with that that and i was a very happy client. Two weeks ago i noticed that my account was being overdrawn and i tried to call the call centre at first i ran out of airtime while i was holding and the second time i was put through a long list of security questions and at the end i was told that i had failed two security questions and therefore i cant be assisted, being frustrated i asked that lady how do they work my account is being **********ly used and she is telling me she cant assist me because i failed 20 out of 6 security questions and she promised to called me back and she never did. i then wrote an email to the business manager charles malatsi at bankcity where my account is being held and he never rep**** and i wrote again but still nothing . i then called the bankcity branch and spoke to a guy who told me to go to my nearest branch to get the matter sorted. i knock off late and i havent gotten a chance to go the the branch and in the meantime my account is still getting over drawn. im so disappointing with the customer service at fnb and i want them to sort out the mess on my account with immediate effect