I called it back. You get a recording saying that either everyone is busy, or you called after-hours or on a holiday, and to please call back during business hours and they are very sorry they missed your call. They want you to leave your complete name and address, along with your phone number. No key option to opt-out of this number. They use a lot of different phone numbers with different prefixes, and it is the same recording every time. I just blocked it permanently.