Ah, "Card Holder Services" that needs you to give them your credit card numbers, expiration dates, and security codes "for verification" to get the 4 1/2% interest rate they are offering...
These criminals work out of south London, England using VOIP. They are linked to Pakistani terrorists and folks they dupe get charges from all over the Middle East, mainly from our "allies" in Saudi Arabia and Pakistan.
The whistle or boat horn is the absolute best approach. Never give out your credit card info. If it was really your bank offering you a good deal (like that is ever going to happen!!!) they would ALREADY HAVE your information.
You are SO RIGHT! Most of these scams are outside the U.S. If you cannot call them back on their Caller ID# it's 100% that they are CRIMINALS. But turning them in with a DNC Registry report gets them into the system and over time will get them busted. No, not in every case - BUT IF YOU CAN'T BE BOTHERED TO MAKE A REPORT THERE IS AN ABSOLUTE 0% CHANCE THEY WILL EVER BE STOPPED.
Clearly you do not understand how the DoNotCall Registry works. The Registry works on voluntary compliance like speed limit signs on highways. Honest telemarketers honor the Registry, abusive telemarketers and scammers do not. Socialist Europe has opt-in marketing where telemarketers are forbidden from calling you unless you give them express permission beforehand. Capitalist USA has opt-out marketing where telemarketers can call by default and it's up to you to get them to stop calling if you can. Big business and the Republicans fought against the creation of the Registry and we are lucky to have what we have today.
Socialist single-buyer health care systems in all other industrialized countries cover ALL their people for a few percent of GDP and paid for through taxes. Our capitalist you-take-your-chances health care system covers ~5/6 of our people for ~twice that and God help you if you have a preexisting condition and no insurance, or if you should lose your job and lose your insurance and then get sick. Yes, you should run away screaming from our healthcare system.
The DoNotCall Registry works on voluntary compliance like speed limit signs on highways. Honest telemarketers honor the Registry, abusive telemarketers and scammers do not. It's not that the Registry "is not enforced", the Registry CANNOT be enforced because our phone system is an "open" system where anyone with a phone and phone line can call anyone else in the world.
People, people!! Just ignore these scumbags. I usually set my phone to "silent" and calls like these don't bother me as much. Complaining on these forums let you get off some steam but will not stop the calling.
If someone really needs to get a hold of me, they will leave a message. (try it, it works!) I wish there was a nationwide consortium to not answer these calls, ever! and you'll drive these idiots out of business.