Truecaller - Find a person by a name or phone number worldwide for free using Truecaller.
YouMail - YouMail turns visual voicemail into a personal assistant for handling all your missed calls.
CallApp - Free Caller ID & Call Blocker app that allows mobile users to block phone calls, identify calls, blacklist unwanted callers and much more.
Hi Voicemail - Stop robocallers filling up your voicemail
CallerSmart - CallerSmart is an application that is basically used for the purpose of looking up mystery phone numbers for free.
MightyCall - Virtual phone system that lets you run your business from anywhere.