Maybe the bill had already been paid but improperly recorded. I’ve had that happen several times. I also received bills for body armor that I did not order nor did I pay for it. I ignored the repeated bills and waited for them to try to contact me by phone which they did. The bill was for a police officer in another state with exactly the same name (not a common name either). The idiot collection agency simply did an internet search and found my name; assumed the customer was me even though they sent the product to another state. I have also had bills sent to addresses other than mine and I did not have any way of knowing that the bills were due or past due.
“Maybe the bill had already been paid but improperly recorded”
We have one of those too: Early 2008 hubby had back surgery. You couldn’t see the doctor unless you paid FIRST!
12 months later we get a bill for the last visit before surgery. Thought it was handled. Then in January 2010, we get a bill with a slip attached “This statement has been audited for accuracy”. We laughed at that one.