Samsung Infuse 4G doesn't run on 3G
I have a Samsung Infuse 4G, model SGH-I997R, which normally runs on the Rogers network. Whenever I'm in an area that has only 3G, I can't use the browser or receive email. And now I'm visiting in Australia, where Optus has only 3G. And it doesn't work. (It worked on my last trip here, when I used a Telstra SIM card, but I can't remember if Telstra as 3G or 4G.)
I've contacted Optus, and they walked me through a number of settings, with no luck.
Anyone have any ideas as to how to get my phone to work on 3G? If not, I'll have to dump the Optus SIM and buy a Telstra one, which doesn't have nearly the same data or voice capacity for the price.