Truecaller app is blocked in Pakistan, website is also not accessible in Pakistan. Its famous app to identify names of unknown callers, who not even saved in your contact list.
When someone install truecaller app his/her contact list saves in truecaller server, when anyone of them call to anyone who has truecaller app installed will be able to see caller name that you have chosen while saving his/her number.
Its kinda privacy breach that without any consent of person his/her number is listed in database and anyone can see name of the person by just visiting truecaller website and do the mobile num search.
Reasons of this recent truecaller ban in Pakistan is still unknown. Truecaller support team on twitter replied to queries that it’s not the problem from their end so they cant give any estimated time when will it be resolved.