SHOCKING SHOCKING Service!!!!!!

I accidentally clicked on one of these loan companies a few years back and didn't read the small print, I never went through with the loan and just forgot about it. I then started to receive very threatening emails and I entered into to a payment plan. Months went by and assumed I had paid off what they said I owed. I then receive another email demanding payment out of the blue. After trying to call on numerous occasions with no answer, I finally got through to the one of the rudest men I have ever dealt with. He proceeded to tell me that there was a problem with their debit orders so only 3 payments were taken not six. When I asked why the email didn't say that and why it was so aggressive he proceeded to shout at me on the phone, interrupted me, would not let me talk, sighed while I was talking and when I told him to watch his tone with me he hung up!!!!! It is SHOCKING! Please can I have some sort of advise on how to proceed. They keep saying they will blacklist me. Can they?