I won't go into account details in a public forum, but I hope you can use these three pieces of info to gather what needs to change.
1. MMS absolutely requires an active data connection in order to download.
2, When your account reaches 5120 MB, by default we have a cap that suspends your data.
3. On our CDMA network, sometimes you need to reset provisioning with *#*#72786#*#* when your data gets suspended in order to update your profile.
As long as the CDMA profile is reset, you should be good to go. If you're not, give our support a ring and we'll help get your MMS working again.