Sharp Hiptop 3 / Sidekick 3

Hey, I'm wondering in case anyone knows about this.. can hiptop 3 be used overseas with other sim card? Will the whole phone works or just the internet function that won't be able to work?

I ask the people from Telstra (in Australia) who sells this phone, but they have no clue whatsoever.

Thanks all!

Very appreciate the feedback!