Canadian response, "I'm not interested." Hangs up.

I take the view of the social contract: if they won't respect the rules and are impolite to you, they forfeit their right to politeness back. You're perfectly justified in hanging up on someone if they're so rude as that.

It's also true they're just doing their job, but that just makes it more okay to hang up on them. If anything, you're helping them hit quota by letting them move on quickly. It's a service!

rather than asking when would be a good time to call back

This is the most British response ever...

Please call me back and harass me later when it's slightly less inconvenient

We have an automated sin bin extension that we transfer these calls to as soon as we ID them as crap. It's usually shipping accounts, Chinese factories and forex these days.

It goes to a voicemail that politely tells them why they are there, to remove us from lists & to leave a message/email if they think we've mishandled them.

Repeat offenders have their numbers filtered to only ever go to that extension. We don't get much trouble on the phone these days, and nobody has to waste their time with niceties when we do get unwanted calls.

Thinking about spinning up another that just repeatedly hurls abuse in Hindi for the scam energy calls, which all tend to have geographically similar origins.

They don't necessarily want sales, they want call numbers. These poor dipshits sit next to a phone with an auto-dialer and just talk to whoever is on the line. They probably get paid by the number of calls they can make in an hour.

My cell phone doesn’t even ring if you’re not already in my contacts.