Posted By RichC on February 3, 2010
To prevent this, call the following number from your cell phone: 888-382-1222.
It is the National DO NOT CALL list. It will only take a minute of your time.
It blocks your number for five (5) years. You must call from the cell phone number you want to have blocked. You cannot call from a different phone number. It takes about 20 seconds.
See a previous post.
UPDATE: THANKS for the Snopes.com link Eric! (comment below)