getting this from "Agent 7 (or 8 or 9) " twice a day...and now is using a local number. I tried this strategy:

Three Little Words That Work!!
(1)The three little words are: 'Hold On, Please...'

Saying this, while putting down your phone and walking off (instead of hanging-up immediately) would make each telemarketing call so much more time-consuming that boiler room sales would grind to a halt.

Then when you eventually hear the phone company's 'beep-beep-beep' tone, you know it's time to go back and hang up your handset, which has efficiently completed its task.

(Hopefully, this will deter the 'agents'.)