Breach of Contract

on Thursday the 22/10/2015 I received an sms from old mutual finance advising that they will run a debit order from my personal account, I then phoned their customer care center on *** and spoke to a guy by the name of Dean who told me not to worry about the sms as the agreement between me and old mutual is for them to debit on the 25th of every month. today when I woke up I received an sms notification from my bank about unpaid debit order that old mutual did on my account and as a result I've been charged unpaid item fee and my account is in a minus because of a debit order that old mutual submitted and it also affected my credit score as it looks like I'm someone who is irresponsible and can't manage his finances. this ****ed me off cause it's not the first time old mutual is doing something like this, last month the did the same and this time they went beyond as this debit order they submitted is in contravention with payer's authority and against the credit act. I demand something be done about this.