CallerSmart - CallerSmart is an application that is basically used for the purpose of looking up mystery phone numbers for free.
Castle - The easiest way to protect your users from getting hacked
Truecaller - Find a person by a name or phone number worldwide for free using Truecaller.
You've Got Spam - A new tool that lets you spam back the spammer
ThisNumber - ThisNumber helps you find phone numbers for people and businesses!
Sync.ME - Search over 1 Billion phone numbers worldwide. Identify unknown phone numbers and block unwanted calls.