What are my options to block someone from calling my number?

The secondary line on my plan seems to have formerly belonged to someone who stopped paying all their bills. Most of the numbers calling looking for the previous holder of the number are blocked, unavailable, etc. All of these agencies keep telling me they'll "put a note in the file" that the person they are looking for is no longer reachable at my number, but they keep calling. As long as they block their numbers, I can't find out where to send a cease and desist calling letter. This has been going on for months now, and it's getting old. They're using my minutes to basically harass me looking for someone I can't help them find. Outside of flat changing the phone number and risk getting the same problem with a new name, what can I do to stop these blocked numbers from getting through?
Labels (1)