sk4g not sending/recieving mms properly

[superman8589#AC]

okay i purchased my sidekick 4g the other day, when i purchased i placed my "simple mobile" sim card in, and i did all the data settings right got it from the simple mobile site, as soon as i set it up i rebooted the phone, and tested the web and it was running on 4g just fine, i called my wife whom has a sidekick 4g as well but on tmobile worked as well sent her a test text worked as well...so i decided only thing left to try was mms, i sent her a pic of the malls parking lot... she recieved about 10 min later (ya rather late but who cares as long as they get it right? ) okay so when i got home that night i took her phone and was trying to send photos to my phone from hers, they would come in but when i would hit download it would say downloading then after awhile just say downloading of message from holly was unsuccessful, and now i have noticed it dont want to let me send any mms and ill recieve the mms but wont download, please help, i dont know how to fix it.