Bad customer service

I had a bad experience with MBD Credit solutions (Woolworths).Ive arranged for a debit order to cover the arrears.My problem is,they keep on calling me day and night to threaten me . .The last consultant spoke to me is Meryl who was very rude to me.I even told her that I expect them to call me if the payment didn't go through.I really feel that my consumer rights has been violated in this regard.Please enquire for me why are they doing this though I've arranged for a Debit order