Supposedly the hardware supports all the frequencies (according to motodev and similarities with a853), I've just never seen anything other than 1700/2100 and I know a lot of people have struggled with this.
XDA Developers was founded by developers, for developers. It is now a valuable resource for people who want to make the most of their mobile devices, from customizing the look and feel to adding new functionality. Are you a developer? | Terms of Service