I can only send/receive MMS (sms works fine) using the default messaging app Samsung includes with the S4. Any of the other apps I've tried will just say failed to download/send message, retry? I've tried plenty of guides that try to fix MMS. Ones that tell you to do a carrier profile reset, update the prl make sure the apn is correct, ect. But most of these guides amuse MMS is not working at all. For me it seems to be an app issue and google doesn't seem to return anything for my specific problem. I'm on Ting, which is just re-branded Sprint but I don't think that matters since another phone on my account doesn't have this problem.