As nice as this would be, as an American (notably not a Frenchman), I find that 90% or more of the unsolicited calls I get are scammers, not telemarketing, so I

As nice as this would be, as an American (notably not a Frenchman), I find that 90% or more of the unsolicited calls I get are scammers, not telemarketing, so I don't know how much something like this would do. The US also has donotcall.gov, which no telemarketer bothers with.