I answer the phone, and when they tell me which company they're from I cut them off and tell them I'm not interested and would they please remove me from their calling list. Then I hang up.
If they call back (which sometimes happens) I remind them that their company can be fined for calling me after I asked them not to and again, I hang up.
There's usually not a third call. If there is, I tell them that any company that calls me three times after I requested them to stop must be completely unorganized and I wouldn't want anything to do with them anyway.
There hasn't been a fourth call. Yet.