How to Track Unknown Numbers on an iPhone
The iPhone doesn't offer a way to block calls from unknown numbers. However, you can track unknown numbers to determine if the calls come from telemarketers, scammers, or pranksters. A phone number may appear that you don't recognize; other times, the iPhone screen may simply say "Unknown." If you can see the phone number, you can track it.
Tap the "Safari" app on your iPhone to open it.
Enter the phone number into the search bar. Tap "Go."
Look through the Google search results. If the number appears on a company website or a personal profile, click the link to see who called you. Alternatively, if the link appears on a spam-reporting website, click the link to see what other users have said about this number.
Tap the search bar in Safari. Type "reverse phone lookup" and press "Go." Click one of the listings, such as Intellius, White Pages or Reverse Phone Directory. Enter the unknown phone number and click "Search." Most websites require a fee to track a number. Use caution if you decide to pay for this service. Some sites may be scams.
Tap the "Phone" app on your iPhone and tap the "Recent Calls" button. Tap the unknown number to call the number back. You may get an answer or an automated message that explains who is behind the call.
Alert the police and your cellphone service provider if you receive harassing calls from unknown numbers.