I have recently upgrade to the S4 on Sprint. The first app I downloaded was GO SMS Pro to act as my default messaging app. I am able to send SMS messaged with no issues but am unable to send or receive MMS. I have since removed the app and gone back to the stock S4 messaging app. I would really like to return to GO SMS. I have done a digging around the interwebs and tried a couple troubleshooting ideas but nothing has worked (Manual APN, Turned off WIFI, Uninstalled\ReInstalled GO SMS Pro app).