Frontier including junk mail in our bills.

I was already having issues with Frontier, but this is just sad. I was just remembered of this after finding my bill for my customer ID. Along with our Frontier bill, we receive junk mail, advertisements, and Victoria's secret adverts. This isn't your standard junk mail either. We got an invalid check for 100 thousand dollars in the Frontier bill. On the back it stated in red 'INVALID SEE OFFER BELOW' with a 100 thousand dollar life insurance policy from a company I have never heard of... I am NOT making this up I swear to god. Does anyone get this with their bills? Location: Western Wisconsin