Scam

I received a call saying that I am getting a $7,000.00 grant that I do not ever have to pay back. Then they give you a security code and a Phone number to call back and give that code to the person who answers.  Then they want you to pay $180 dollars to receive it but you will get that $180 with the $7,000, so you really end up with $7,180.00.  I did think this was a scam so I asked how can I be sure that this is not a scam and they hung up after they said that it wasn't.  Sounds to good to be true.