I have a family texting bundle with att but i cant send or receive multimedia messages?

On my att plan we have a family texting bundle witch includes three phones,mine,my husbands, and our 14 year old daughter, My husband and myself can get multimedia messages,bur whenever our daughter attempts to receive one it tells her that it isn't an available network barrier. She has a Samsung Magnet and on her plan it says that she does have multimedia messaging and her phone is compatible. Does anyone know how to fix this? It is very annoying for us. Her friends and boyfriend are always sending voice messages and picture messages to our phones and we want her phone fixed.