Debit Order on 24th before pay date 25th

I have a telkom mobile account which I pay by debit order every month, dated the 25th. In July, the 25th was on a Saturday but my telkom mobile account was debited the day before, Friday the 24th. I wasn't even aware of it as I assumed that it would be debited as it normally was and admit to being irresponsible by not checking my debit orders one by one but I feel that it is unfair that I have an 'UNPAID' debit order, giving me a bad credit record, when the date decided on for the debit order was on pay day, the 25th. My accounts are all paid by debit order and I cannot understand why most of them went off on the 25th or the Monday thereafter, but telkom mobile the 24th. Furthermore, my services were suspended, which I understand because I didn't make a payment, but I asked if they could debit the full amount this month. The answer was no, they will only debit this months account and the rest has to be paid into their account and once it reflects, it goes to a department who will look through everything and thereafter it will take 72 hours to a week to have my suspension lifted. Not nice!