Consistently get a blind - dial "Unknown Name" with 321-304-9999 as the id.
Pressing any button seems to put me in a queue to talk to someone, but never seems to go thru.
I'm on the do not call list, which would be enforced by the government, excepting that the entire bureau has been gutted by the last administration. Not to worry though... when I find the location...
Press the option to speak with someone and then lay the phone down. Make them rack up huge phone bills. They'll stop calling only when they can't afford to bug us anymore.
The Government Do Not Call Registry hasn't been much help (typical government). These peope call me daily and I report them daily. Do what Doug says: Press the option to speak with a representative and then lay the phone down. This way, they get annoyed and will have to pay more for the phone call.