harrassing phone calls

Allied Financial has been calling our phone number for years. At least once a day, sometimes more. We are sick of this. I have tried staying on the line to talk to someone to ask them to stop calling and when I get a person finally, after waiting 20 minutes or more, they hang up on me. Do we have to change our phone number to stop them? Or do they call everyone, everyone using the phone book? I signed up for the "NO CALLS' thing. It seemed to help with other type calls, but not this Allied Finance. I wish we could just not have a phone anymore.