Could be sloppy record-keeping or the hospital is just trying to cover all its bases.

Just because a voice on the telephone claims you owe a debt does not mean you owe it
If a voice on the telephone claims you owe a debt:

1.    Demand the person give you his or her name, company name, and address
2.     Demand a debt validation letter by US mail.  E-mail no good.
3.    Do not pay  the collection agent or anyone else a  DIME  until the debt is validated.

They should have sent you some written documentation about  your bills.

If they are bothering you,

Report them:

http://www.consumer.ftc.gov/articles/0149-debt-collection

Also contact your local attorney general

this number called me no answer no message I'm in California

Got a call also, rang twice, hung up left no message. Must be telemarket or scam.

Yep, left no message, third call from California in two days! Must be a major chain that was hacked, I am not a shopper!

missed call 2:23 no message.  I have kansas phone number.