In our experience pressing any number to stop calls works exactly the opposite. After all, these are criminals calling you who do not obey any laws, so why should they honor your wishes? Also it proves to them that they have a working number with someone who will answer. Read notMicheal's post.
A number from Montebello, CA has already called me 5 times today. I asked them to remove me from the list and the agent stated "expect another call" and disconnected the call. Their caller id states "AUTO"
Call left no message so I called from another phone. Heavy accented man. All I could discern was auto something. I told him I did not have a car so I could not understand why he was calling me. He said that he had information on me and hung up.