Reaping people off

What a useless bank thinking that they will reap people off... I had an account with them with overdraft that I never used so they are threatening me that I will be place under SECTION 71 OF THE NCA because I am not paying the interest on overdraft and I questioned them "did I took any credit with them if I never used it? The contract says I will be liable if I use the credit. What a useless **** of bank. Big name but reaping people off.