If someone calls you with an offer, don't trust their call, you can't be sure they are legitimate.
"Call them back. Again if someone is selling you something or asking for information, tell them you will call them back and then either verify the company is legitimate, or if it's a bank or credit card company, call them back using a number from your bill or your card. Never provide credit card information or other private information to anyone who calls you."Source: Protect yourself from vishing attacks | Tech News on ZDNet
