Overcharged; sales consultants not disclosing charges when opening accounts

I have an account with FNB; I have been tolerating their expensive bank charges but I was shocked when my account is sitting on R-600 but the last time I checked I had R400. apparently all the purchases that I made almost 2 weeks ago only went off now. And I am charged R100 for each transaction. I want all these bank charges to be reversed as I can not pay for something I dont know and I'm gonna close my account soon with you people. I once had an iPhone which you refused to pay the insurence when I claimed. I am so tired of your exploitation.