Simply enter the phone number at any payphone from within the game to unlock a collectable and remember there are acheivment points for collecting 1, 25, 50, and 100 collectables. Thats 4 EASY acheivments totalling 40 points, not to mention the hours of searching to find the numbers in game!

Effect - Code

Collectable 01 - 5554463
Collectable 02 - 5554525
Collectable 03 - 5554565
Collectable 04 - 5554569
Collectable 05 - 5554603
Collectable 06 - 5554649
Collectable 07 - 5554676
Collectable 08 - 5554682
Collectable 09 - 5554691
Collectable 10 - 5556118