This number calls me at least 3 times a day. Wish I knew who it was so I could report them. I like Puzzled Dude's comment about pushing numbers on the phone to make it think you are a fax machine. I'll try that next time.
Fax machines are cheap. My all-in-one printer has one built in. I just hooked it to my phone line and leave the "auto-answer" on during the day. all the robocallers that call the phone (regardless if i'm in or out) get an actual fax machine and thus delete the number from their databases after a few tries.