It's K12......if you have ever shown an interest in homeschooling......they will HOUND you.
I've asked them to stop calling 20 times now and STILL they call.  6 times a day sometimes.  I've had my phone just "block" the number.  It's my cell so it's easy to do.  
If you call them directly and ask them to take you off their list.....they have 30 days to do so.  THEN you can threaten them with harrassment....(not that it would do much).

No message.  3 days in a row.

They've called twice today but won't leave a message.

keeps calling no message