I have a pre-paid cell phone that costs me $15 a month and I'm thinking that the reason it's so cheap is that my provider sells my number to... everybody. I get more garbage phone calls on it than I have ever had on any phone. In spite of the fact that I owe no one a dime (except the library... oops!), I get three or four debt-collectors (looking for Brian or Stephen, whoever they are) threatening me every day! (Well, they would if I still picked up.)
Maybe you're not as stingy as I am and you pay your cell service to block junk calls; still, your computer isn't safe. I bet you've had e-mails from foreign dignitaries down on their luck and looking for a place to park their multi-millions. They'll pay you an enormous fee if you'll agree to babysit their fortunes just until the heat is off. All they need are your bank account and social security numbers. I've had letters from deposed princesses, heads of large corporations on the lam, dames and earls, and not a one of them can figure out how to open a checking account without my help. It's no wonder they're in trouble.
There's no better advice for dealing with scammers than this: just hang up or delete! But if you want information of greater depth, the library has books on the subject. Here are some of them: