If you don't hear a dial tone on any of your landline phones and your phone service is down, first check for area outages using the Outage Tool. If there are no outages at your address, the next thing you can do is use Troubleshooter to help you identify problems with your service.

After you have hung up on a harassing caller, or after the call has stopped ringing, pick up the phone again and listen for a dial tone. Dial *57. You'll receive a recorded message with additional instructions for tracing the call. 

You can block unwanted calls by using calling features to block incoming calls, adding your number to the National Do Not Call Registry, using a call blocker device, or changing your directory listing so it's harder for unwanted callers to find you.

This calling feature keeps redialing the number every 60 seconds for up to 30 minutes. To activate it, simply hang up when you get a busy signal, then dial *66 and hang up again. When the number you are calling is no longer busy, you'll get a short-short-long ring on your phone. Simply pick up to connect the call. Read more about Continuous Redial.