Around the World

I've just purchased my first GSM phone, Nokia 6820 with ATTWS service.

I am traveling to the Philippines and Japan and would like to get a pre-paid SIM card since roaming charges are quite high. I just don't know if I can do this.

Could someone offer some insight on this. From my research, it looks like my phone is "locked this mean I cant use a pre-paid SIM?

Thanks for the help!