ATT/CINGULAR Unlocked Phone Problem

I have an old AT&T sim card and am trying to configure my new unlocked PEBL to receive MMS on the cingular network. Will the Cingular configuration for the phones work or will I need to find the old AT&T ones? Any help is greatly appreciated. I've been trying to use the Cingular configurations on the website, but haven't had much luck. If anyone has had luck with this, please point me in the right direction. Thank you very much.

U will need to find AT&T configurations. Should be able to find them in this forum, I would think.