randon deductions as pleases

i opened an account a few months ago and signed for a deal to deduct R299 per month off, they have been deducting R349, i then added another unit and signed for R799 pm, this was all a debit order on a specif date, they now in the middle of the month deduct over R1400 without notification nor explanation, i want this put back into my account and when i asked about it they said no payment was made, yet i see there was payment and it is a debit order that always has funds in the account, honestly just a *******. i never authorized that amount nor that date so how can they just willy nilly deduct from my account