Annoyed

I took out a contracted in 2016 around September and I have never had a problem until now, I realised that my Telkom debit order didn't go off on Monday usually when my pay date falls on the weekend the debit order will go off the Monday. I called in to enquire after I received an sms stating that my account will go to the lawyers, I got an explanation from your consultants that my account was debited on the 24th already and there was no money because that is not my pay date, what I dont understand is why now, it was not the first time I get paid on a Saturday and my debit only goes off Monday I need a proper explanation where must I get the money to pay if you decide to debit early to my knowledge the naedo system will debit later not earlier. I'm glad next month the contract will be finished