Reason for contract application declined not substantial

I am a loyal customer with Cell C and I currently have a data contract with them. I app**** for another contract and to my suprise my application was declined. I called in on the 13th of Feb to find out why my application was declined and I was told that I had an unpaid amount/amount in eraear on my bank account. I then check my bank statement to varify what I was told as I know that I pay my debts on time. To my surprise the unpaid amount they are refering to is a reversal of a debit order back into my account as the debit order was unauthorised. So my question is, was my credit check done thouroughly, or only my bank statement was varied to do the credit check. The person who reviewed my bank statement did not review it in detail becasue if that was the case, they would have seen that the "unpaid amount" (which is the description of the transaction) was actually money coming into my account.