I just explored truecaller online (not the app) and found that out of two numbers that I searched one was correctly reported and the other showed some other name altogether.
How this truecaller actually captures the mobile number details? I wonder because the other number should ideally have been reported correctly.
Okay... 1st of all every apps get permission for whatever media/app/access required with read/write permissions... when you root your device, there is "App Option" app. You need remove permission for those unnecessary things,... like your browser get permission for "read" "contacts", then just turn off permission like this..
*i.guim.co.uk/static/w-620/h--/q-95/sys-images/Technology/Pix/pictures/2013/12/20/1387523152901/app-ops-3up.png
now for truecaller...
that service read your contacts after your installation and upload it to their server... just like that they read everyone's nos and upload it..
okay.. so now for lollipop it was rumoured to come without root.. but you need to root lollipop for that...
any further questions...???