They have called me several times trying to push some kind of home security system on me. Every time they call I tell them to take my number off the list, yet they keep calling back.
I just started calling them back non stop, and even when they don't answer I just call back again. Probably around a 100 times. I think they got the point because they haven't called me back since.
What I do if I have an Android is take your number and put it to a no ring mode. IPhone is better...I just go to my recents then press block. As to purchasing a call blocker...how are they gonna know...they change their numbers like the wind. I just take note on the first call...then block