Getting contacts off your old mobile phone and onto the iPhone may or may not be a straightforward process. If you already have your contacts stored neatly in Outlook (Windows), Address Book (Mac) or a Yahoo!/Gmail Address Book (Mac/Windows), the process is as simple as syncing via iTunes. If all you have is a set of contacts stored on an old Nokia 6300, however, the process is a bit more involved.
Edit: To complicate things I have no budget (so I must rule out paid for Apps)
Edit: I don't live in America, so suggestions in other forums saying "Just take it to AT&T" don't apply to me
Best Answer
There is a iSync plugin for the Nokia 6300, you can find it here. Once you have synced your contact to the Address Book on the Mac you can use iTunes to sync the contacts to your iPhone.