they get your number through anything you provide your number for. state licenses, professional associations, freakin amazon.com probably too. they all sell your information. I -never- got calls like this until I joined my professional association about a month ago, and this is the third i've received. its ridiculous.
I got a call from this number and pressed 1 as soon as I heard the "this is Amber" message going. I was on hold for 5 minutes, 10 seconds before "Wade" answered. He was very polite and asked how he could help me. I told him this was third time I had requested removal. He took my number down and said I was removed.