Why can't I receive emojis from an AT&T iPhone on my Virgin Mobile iPhone?

My girlfriend can't send me emojis through messaging but can on kik, kakao and things like that. We both have iPhones, so I don't see why she can't. Hers is jail broken, but she can send emojis to other people, just not me.

VM iphones are junk and don't support most features.
try to turn on cellular data.