Blacklisted for billing account of 3 years back

I've been renting a flat in Lotus Gardens and when I moved out of the flat I gave notice as per requirements. After a year or so after moving I received a email from Constantia Metering Service saying I owed them for service. Fist and foremost we were using prepaid electricity, and we always had problem with their water billing because they were too much and out of assumptions. I told them the owner of the flat or the people I was renting from were the ones who were suppose to tell them when I moved, because they claimed they didn't know I moved. Now after 3 years out of that flat, I receive a email from TPN Credit Bureau saying I am Blacklisted from not paying their clients. I did tell them that I do not agree or disagree to this, but will first look for further advise on this issue, then if I am expected to pay, I will make an arrangement, instead of them just Blacklisting me. Please please advice.