Wrongfully Blacklisted for an account of 2015 which i never recieved so much as a notification for outstanding amounts!

This Company says I have an account outstanding of the ammount 4500 from the year 2015! I did not have a medical aid at that time and went into hospital with a possible vrain tumor! They never ever followed up with me! I never recieved up to this day a physical statement stating that I do owe money nor an email or so much as a SMS. As far as my knowledge it is unacceptable to "blacklist" someone for an account they wasn't aware of! And now because of this I can't get an account anywhere! How am I suppouse to live and survive as a single mom! I lost my job right after my hospital visit! And the worst of all is that it is not their lives that is affected! All they will say is pay your debt! How am I suppouse to pay it if I wasn't aware of the fact that I had an outstanding account! And they will not try to resolve it! You can't blacklist someone for an account of 2015 that I never recieved communication from! As far as I know that might be ******* as well.