Unless you specifically go on-line seeking to buy things like life and health insurance, I would say that 99% of those unsolicited calls you get are from companies that are only trying to get money out of you without providing you with any kind of service in return. In other words they are crooks. Let me give you some examples on how you can tell if these calls are legitimate or not.
One common one that has been around for the last five to ten years is one in which you get a recording offering to lower your interest rates on your credit cards. Although the recording gives you an option to opt out from receiving any more calls, they continue to call you from two or three times a week or at least once a day.
If you get a person on the phone, they will either say that they will take your name out of their data base or will curse at you or just hang up the phone. When you try to call back to complain, you find out that it is only a one-way number. Although the feds are working on putting these types of illegal business out of business, it has not been an easy task. The best solution is to just not answer the phone calls.