Check with your existing wireless provider for contact backup options on your current device.
If you already keep your contacts on your Mac® or PC, you can use iTunes to sync them to your new iPhone.
Note: iTunes syncs contacts with applications such as Mac OS® X Address Book, Yahoo!® Address Book and Google™ Contacts on a Mac; or with Yahoo! Address Book, Google Contacts, Windows® Address Book (Outlook® Express), Windows Contacts (Vista® and Windows 7), or Microsoft® Outlook 2003, 2007 or 2010 on a PC.