iPhone 4S group messaging doesn't work on straight talk

[barefootgirl123]

i unlocked my 4s and switched over to straight talk a few months ago. i'm happy with almost everything, but i just discovered my group messaging doesn't work. I changed my APN settings, to where my data works, and i also jailbroke and my picture messaging works, so i don't know why the group MMS doesn't. i've tried it where all the recipients had iMessage, and that worked fine, but not as MMS.