Nedbank unable to deliver service.But Able enough to charge a excess fee!!!

As a micro business I really feel that Nedbank is all out to cripple micro entities.. I have been having a ongoing problem running from pillar to post.. with no help....Firstly nedbank says that my business cheque account was in excess of R6000..which is very confusing to me as it is a cheque account and according to me and my proof from the SMS I recieved from nedbank regarding every transaction I done..it is merely impossible for that to occur...then now i am changed R149 per day for a excess fee which is unfair...I have made numerous queries with my business banker and no help..I have been to the Mall@redds branch and spoke to Sindi...still no help...what should I do...you have taken more than R2000 for excess fees and a mere R6000 for something which is unexplained.. I really need assistance with this Asap.i pay banking fees for a reason..so help...and being closure to this ...as it is affecting my business..PLS PLS PLS HELP