I'm in the US, have had the same cell phone number since 2004 [1], and have put it on the do-not-call list, and it doesn't seem to have made a difference. I receive 2x as many junk calls as legitimate calls, but at least an unknown number in my cell phone's area code (where I haven't lived since 2007) is a strong signal that its nobody I want to talk to. (But I can't tell my phone to filter unknown numbers by area code)

[1]: https://xkcd.com/1129/ applies well to me.