Unfair treatment

Debit order of R774 was not honoured and I was charged R115 admin fee. Not making sense is - I deposited only R80 to have a balance of R848. It means the debit order was unfairly not honoured. If I was not charged R115 admin fee, I would have a balance of R963, more than sufficient to cover the D/O of R774. The question is “why my debit order was sent back, when I had sufficient funds?”