Zenith Bank Of Nigeria — Unauthorized deduction

I made interbank dollar transfer, that was supposed to cost $7.5 but $100.00 was deducted from my account, all my effort to get the fees reversed proved abortive.
I transferred $1600 from my donicillary account, which the fee supposed to be 0.5% but $100 was deducted from my account .
The manager and the staff was disrespectful and uncooperative in resolving the issue. All they said was it's the computer not us.
I need the fee reviewed and debit my account with the over charge fee.