Outstanding money to be paid

Am really not happy with Outsurance after cancelling them and having a hassle with them for some time and finally it happened. Then to my surprise when I wanted to open an account am told that they have listed me on TransUnion for an outstanding money I didn't pay. Am shocked because after all the bad service I've received they still say I owe them :(. Why didn't they make a follow-up with me on this or is it a way of making sure nothing goes well with me.