mobile

I feel like this is probably an easy fix, but I cant seem to figure it out. My phone wont recieve MMS UNTIL I make/receive a phone call then i get all my MMS messages at once. Im on LTE/CDMA with data off and wifi on when this occurs (not sure if this occurs with wifi off yet) . Only once did i recieve an MMS without a phone call and that was at a random time 4 hours after the MMS was sent from my friend (no settings or data connectivity were changed within this time)