The call is in Spanish and says something about $100 worth of gas! Very annoying and there's no way of calling them back to tell them to stop! When I called them back the phone made some sort of dialing noised and hung up.
How can I get these people, (calling me on my private cell phone costing me money) to stop?

Isn't this illegal?

The call is in Spanish and says something about $100 worth of gas in an annoying and loud pitch? Not only is it a solicitation for a marketer but they're calling my cell phone number costing me money for nothing!