During practice I once managed to accidentally call the security line early, because I was on a different savegame than I thought. It was during Part Three, so that confirms, that you don't need to read the book with the number to be able to dial it.

In theory you could try to guess the numbers of the security or fan service lines during the 10 minute wait for the agents' return. So I started writing down numbers from runs and my practice. I'll put the list here, in case anyone wants to further work on it.

• 1213 fan
• 1479 pidgeons, bank, security
• 1929 bank, security, fan
• 2067 bank
• 2242 fan
• 2339 bank
• 2493 lawyer
• 2686 lawyer, security
• 2783 pidgeons, lawyer(2x), fan
• 3750 security(2x), fan(2x)
• 4355 bank
• 4424 pidgeons, bank
• 4612 security
• 4616 lawyer, security
• 4735 fan
• 4739 bank
• 4753 pidgeons, bank(2x)
• 5042 fan
• 5533 bank
• 5770 bank
• 6953 security
• 7031 security, fan
• 7430 pidgeons, lawyer, fan
• 7531 fan
• 7685 security
• 8429 bank