Your intention might very well be good but this is very bad advice, please do not install Truecaller! This app is a privacy nightmare. From accessing your phonebook/contact info to location, it has been known to be responsible for leaking information of journalists and for storing user data without consent.
> While TrueCaller may have laudable intentions, the privacy implications for people who end up in their database raise concerns. When a number is tagged, the person who is tagged ends up having their name and phone number stored on the TrueCaller database, despite not having consented – or even being aware – that their data was collected.