You are right about those warranty calls always being a scam. Most companies would contact you by mail not phone. And the consumer guy on our local news said there has been a rash of them lately.
Scammers are crooks and don't play by the rules so they will continue to call even if you are on the Do Not Call list. And that thing on their messages that says press such n such a number to be removed from their phone list will only take you to a number where the person will try to sell you something or get credit card or personal info from you. The scammers also cloak their originating phone numbers so they don't always appear on caller id or *69.
Here are 2 places to lodge a complaint:
If you do have caller id and are getting calls you aren't sure are legit you can either put the phone number (ex: 800-123-4567) into the search box at google.com and see what comes up. Everytime I have done it it comes up with one of several sites like http://whocalled.us/ where other folks register numbers of the bad phone callers. But please be aware that the phone numbers they say they are calling from can be spoofed...they are scammers remember...and the so called charity organizations they work for are either bogus with names similar sounding to legit ones or they give pennies on the dollar to the charities they say they work for.
We have voice mail so I screen calls through that and that helps tremendously.
Also be prepared to receive more calls if you have a senior living in the house.
Unfortunately it does not help to be rude to them and they then call you several times in the wee hours of the morning and then hang up on you. I just tell them we don't do business with uninitiated calls over the phone and then hang up before they get a word in edgewise. They will just laugh if you tell them you are on the do not call list...they are scammers.
Some things to do to receive less calls are to check each legitimate business you do biz with and make sure they are not selling your info to "partners"...you have privacy rights you know. Same with charities you give to. Have an unlisted or unpublished phone number. Many people are ditching their landline phones and going with just their cellphones. Don't do phone surveys. And don't fill out sweepstakes/prizes/giveaways form.
Also...telemarketers legally are only sup to call between the hours of 8 am and 9 pm.
Also read this for more info:
Hope that helps! Our calls have gone way down from what they were luckily.