I recently moved my phone number from Telstra to Optus. I don't know quite how long its been with Telstra, but its probably the better part of half a decade and I went in and magically everything was transferred. I must admit it was an entirely painless experience and I even was able to log into the Optus Zoo website (the main reason I switched was that I was one of the original Telstra Prepaid Customers back when it was called communic8 but they still don't have Intl roaming, "our prepaid customers can't afford it", while Optus/Vodafone does (and I really like the prepaid model)).

Its a shame you've been through such a pain though, but I know what it's like to not have your phone with you when you're overseas.