If you are getting calls to your cellphone, surely the number which is calling you shows up on the display. If you don't recognize the number, don't answer the phone. If you are curious about the caller, go google it. If it's someone you want to talk to, simply call them back. If it's someone who was calling you legitimately, they will probably leave a voicemail.
As soon as you answer the phone, you are validating your number to the telemarketers and giving them reason to keep calling you. And if you actually talk to them, you are assuring them that they have reached a real person.
Mass dialers merely make calls to any combination of numbers and there is no way to actively prevent your number from "coming up". Thus, the do not call list will not prevent these calls if they were mass-dialed.
Bottom line...don't recognize the number? Don't answer it.
Called just a few minutes ago at nearly 10pm. I checked here first to see who it could be since we don't know anyone in Los Angeles, which is what caller ID shows. We're on the Do Not Call list.