Is the phone still ringing or has it been switched off? If you have a contract (and not a prepaid account), you might be "lucky"and the theif may have stupidly made calls on your account, in which case you may be able to get him caught. Check with your service provider if the ohone is still being used.

In South Africa our networks are set up to recognise the unique number (IEMI) of each phone. When a phone is stolen it can be blocked and is then useless anywhere in South Africa (Doesn't help get the phone back, but is discourages theft as a stolen phone cannot be sold as it doesn't work!