finding people

I have a lot of contacts in my phonebook. I'm sure half of those numbers are not reachable anymore but for some reason I can't erase them. I'm still hoping that I'd be able to update their contact information. I chanced upon this site wherein they can track people using Reverse Phone Search in the US. You just use the person's old contact number and the site will automatically find the person and not only that, you get to see the person's most recent contact information. Cool eh! You can also have access to their address, other background information and even their family members. If only this service is available in the Philippines, I'd be able to update my phonebook in no time!