ABSA VAF ****TY SERVICE AND THREATS

I've had it with ABSA VAF!! Firstly, they amend my debit order date without my consent. Secondly, I have agreed for my monthly installment to be debited HOWEVER, they decide not to do their jobs or their systems are not working but I get threatening messages about being blacklisted. Then im told that i need to make means to get it paid. This is total bull****!! This is unacceptable!!!