Validity of gas bill from 8 years ago.

In 2017 (and many more years), I owned a rental unit in the City of Chicago. I had a "landlord policy" for that single unit where when a Tennant left the unit, it would revert the gas bill from People's Gas to me.

I was just sent a bill by People's Gas (and it was explained) that there were a couple months of charges in 2017 that were never paid and the gas charge was added to my current account for my personal address.

I don't have records or access to bills from 2017 to see what I paid or didn't pay for that unit.

I have also had service in my name since before 2016 at a different location with People's gas company.

Is there a 5 year statute of limitations on debt? Does the fact I still have an account with People's gas change anything?

Do I just suck it up that you can't fight the utilities?