206-993-XXXX

When I tried to call back I got a recording saying that this was a non existent number.

No message

told me to go to janscashcow.com

Get repeated calls from this number, asking for 'Mark'.  There has never been a Mark here.  Ask them not to call.  They have called up to 6 times in 1 day and when irritated call me an obscenity.  Police can't do anything.  Qwest phone offers to sell call blocking service.  Try filing complaint at donotcall.gov.