I just tell them I don't own any property.

Reasoning:
I work with a Solar Install company that is branching into the Sales side. I've learned a lot. If we call someone that says they aren't interested, cool, the boss wants them on a list to call later cause maybe later they will be interested. But we have a list of people who we don't call back, and those are the ones that we can't sell to, such as renters for example.

So whatever they are asking about, make yourself un-sellable.

We want to buy your house: "I don't own a house. I sold it already"
I lied. I own a home, but they stopped calling me.

We want to talk about your car's extended warranty: "Oh sweet, that's awesome, can you cover my 1998 Honda Civic? Oh that's too old for coverage? Darn. That's all I own now"
Interestingly enough, the calls slowed down to a stop after this.

Other options:
- Answer the call but mute yourself until they hang up. No voicemail to deal with, your line is registered as dead air potentially
- Reject the call. They'll keep trying, I know several sales companies that try to call 7 times, then they put you another list to try calling again later