Register annually to keep those annoying telemarketers at bay. Don't forget the email to click and confirm the registration after you submit your email and phone number on the web page. Register here
Then, create a SILENT ring tone for your phone. No sound. Add a contact called Dirty Filthy Telemarketer
to your contact list. Save any stray calls that might sneak through to that name. Should they ever call again, you won't care because you won't hear your phone ring.