How do I enable MMS on MY unlocked iPhone 3g running on Tmobile 4.2.1?

[Jeff]

I recieved a free iPhone 3G by one of my friends. i restored it, jailbroke it with redsnow b5, unlocked it with ultrasnow repo666 whatever, and am Using a Tmobile SIM card. I dont havre a data plan but i do have unlimited texts and i can call and everything like that. The only problem is that i cant use mms. Ive tried using the tmobile mms 4.0 fix in cydia but that didnt work. it gave me the option to send mms but when i sent a message, it stops at the very end. If anyone could tell me any apps to download, or if anyone can tell me the settings to put in the cellular data network options, i would greatly appreciate it. i am running on Tmobile 3g 4.2.1