Answering a call from an unknown number can be a big security risk. If you do not know the person's identity on the other end, it's best not to pick. On the other hand, if you have picked up the call and do not recognize the other person's voice, end the call immediately. Many kinds of scams can be done over the phone, and it is quite easy to be a victim. Some of these scams require the caller to record your voice or specific uttered phrases. Although some of these calls could be pranks, you should avoid picking them up if you are unsure.