Some of these calls are reverse charge calls. Meaning if you pick up and stay on line, the charges goes to your phone bill. They try to keep you on line pass one minute and as long as possible thereafter. Usually if you hang up within one minute there is no charge. This type of reverse charge exist as a way to charge for tech support services but con artist use this same method to get your money. However it may not work on cell phone plans but it’s a computer that selects the numbers to dial and by chance they might get a # that accepts the charges.