By calling them back you just verified for them that yours is a "good' number and now you will receive more worthless calls. Do not answer call you don't know and never call them back.
This scam method is the MO of the INFAMOUS ***REYNOLDS*** Family group of Professional Scammers. Google their name and you will find HUNDREDS of sites/stories on them. They were supposedly 'shut down' by the FTC in 2015, "Fined Millions" and ordered not to do this anymore. BUT they were allowed to pay ONLY $75,000 *In Lieu Of* the ACTUAL fine, so of course, they are at it again. - I mean, why not? If you can make TENS of MILLIONS and only pay a 1% fine on those spoils, wny not ignore the law and go at it again? This is an example of how the Amoral, CRIMINAL Filthy Rich One-Percenters in this Country are driving it to Hell.