Contacts are just as useful for avoiding those you don't want to talk to. The Do Not Call Registry does not exempt you from certain numbers, namely ones that you have given your number to. So your credit card companies can call you up and try to sell you something or ask you to take a survey that will eat into your minutes. A simple cure for this is to enter the offending number in your Contacts and assign it the image of a skull and crossbones that you can easily find on Google images. Now when they call you know who it is and see the warning sign. It's your personal Do Not Answer Registry.
