We’ve listed four apps to help make the calls stop, and steps to get your number listed on the National Do Not Call Registry with the Federal Communications Commission. Alex Quilici, who works with YouMail, an anti-spoofing app, explains how spoofing calls work. But if you’re using a voice or office phone or call center, you can fill in whatever phone number you want. So the bad guys just pick a phone number and use it,” explains Quilici. You can upload some audio, you can put in a phone number that people “press 1” to and basically go.