I'm trying to conserve data so I turned off Cellular Data from the menu and have been connecting via wifi only. Now, I can't send or receive MMS messages (photos or group texts). Is there a fix for this?
Yes, the 'fix' is to turn on your cellular data. Multimedia texts (picture or group texts) won't send/receive over wi-fi, they require a mobile data connection. However, they count against your text package, not your data plan.
I'm usually connected to wi-fi, so keep my mobile data turned off until needed, such as when sending/receiving multimedia texts. It's not that big a deal for me to turn it on briefly so that those texts can be sent/received.