Truecaller: Caller ID & Dialer
is a caller ID service that allows you to quickly and easily identify unknown numbers that have called you. It is great for blocking spam and any unwanted calls that you might receive. It also allows you to back up your call history, contacts, and settings to Google Drive.
This app is also an SMS identifier and allows you to identify any unknown numbers who have sent you a text message. Spam messages that arrive via text can also be blocked using this app.