From my personal experience I have given this application name as truthteller.the reason behind this is the calls done by mobile company.i use two sim one is idea and other is vodafone.both mobile networks were good but I have to recieve many calls from their network my patience was now low and I was getting irritated because it always rang in class or bus or metro where it is very diificult to see who is calling.i was not knowing about truecaller then my friend told me when I was making fun of tjese companies that there is a application named truecaller it will block all the calls before mobile rings.and I downloaded it from next day there was not even single simple call.true caller worked silently in background and even it gives detail about caller their name place mobile network etc.the feature I liked most was that it also gives photo of caller if you are connected to your facebook id.