Money withdrawn from my account with out my authorization or permission

Good day! I am a client of nedbank, for almost 10 years. I am banking with them. Last week nedbank went into my personal bank account and withdraw money with out my authorization to pay my credit card account that I am having with them. I never gave them any authorization to do so. They never phoned me to come up with an agreement to pay them. They just simply went into my account and withdrew R2000. I gave them a call and I got to speak with a very rude person who told me alot of nonsense and made me feel violated. I am even thinking of leaving that bank and bank some where else.