How to get an iphone to work using a new sim card?

I have an unlocked iphone 3. I moved from America to Australia and I tried putting my telestra sim card in my iphone 3 but its saying it doesn't have any service but the internet works just fine? Can someone please help.

Take your phone to a telstra store. They may be able to help you troubleshoot your issues.

There's no iPhone 3. 3G or 3GS.

It may be a conflict of the bands used. Older iPhones likely wouldn't support those bands. You could check Telstra about that.