I have been using Truecaller since I first started using and Android phones and u must say it saved me alot of trouble a lot of times. Many times some insurance company agents will hound me and the people I don’t want to talk will Call me and disturb me at night which was really frustrating.
I had no option to block calls and had to reject everytime or deal with the person and waste my time which was ridiculous and always thought that if such app ever exist.
Thankfully in Android platform it was available and now I could see before picking up who is that person and if I don’t want I can just reject and can even reject the private number that have no number in them and also the people who are not in the my contacts list thanks to this app. It saved me a lot of trouble.
But yeah I did heard it scans all your number to search for the name of person not having the Truecaller account, which bother me at some point, but it’s still the app I can’t use my android without. So its recommended by me.