I simply do not answer the phone if I do not recognize the number. I noticed a number something like 00000000000000 comes up every week or so, I suspect it is from a USA tele-marketing company, they call freely unlike the Canadian companies.
Do not give your phone number to any company other than a bank, etc. For example, when I return an item to Canadian Tire and have to fill out a form, I always put a false phone number. Why does Safeway need my phone number? Will they call if pop tarts go on sale? No, they take the number and trade it with another company for more numbers and you end up getting a phone call. VD has nothing on these cats!
How Seinfeld handles these calls:
YouTube - How to Respond to a Telemarketer