Not a customer but have a collection notice

I am trying to move into a apartment complex but they say I have a collection on xfinity, I call xfinity and nope they say my account that I had for 1 day is canceled and I owe nothing. Ok well why is it showing I have a collection? They literally told me someone else is at that address and owes the exact amount of money that’s in collection for me!! 
They said there’s nothing they can do since it’s showing 0 amount owed for me. 
What do you mean there’s nothing they could do?? I even spoke with a supervisor and she told me that. I have no clue what to do.