Unreasonable charges

I have a problem with fnb this is fir the second time charging me charges I'm not even aware of.

When I confront them they said there are things which I did not pay and I have paid all my debts but not they are charging me R400 for things they said I didn't pay,can't they check my statement instead of charging me unreasonable.

I'm very disappointed in fnb because I've been their customer for over 8 years but now they are making money out of people.

I'm very disappointed and angry.