Existing PIM data is preserved when registering iPhone
Posted by - NA - on 30 June 2009 04:31 PM
If your iPhone/iPod touch had contact and calendar data on it prior to registration, Contact and Calendar synchronization will default to OFF to prevent existing data from being removed. 
You can enable Contact and Calendar synchronization by enabling them on the device.
  • If you prefer that existing PIM (contacts and calendar events) be removed and replaced with PIM data from the server, turn Contacts and Calendars ON during registration and tap Save. At the warning prompt, tap Sync.
  • If you wish to preserve the existing PIM data, leave Contacts and Calendar OFF and tap Save.

You can change the Mail/Contacts/Calendars synchronization setting at any time.  From the Home screen, tap Settings > Mail, Contacts, Calendars.  Then tap your account.