The end is nigh … Telecom's CDMA network is on its last legs.
If you have one of the old phones you'll need to upgrade to an XT phone (or switch to another network) before the end of July.
You can check if you're on CDMA by calling *333 from your mobile. You then get an automated message telling you which network you're on.
You can keep your number but you can't keep your phone. Telecom has a number of deals to help switch you over – or you can choose another network like Vodafone or 2degrees.