You would have to manually put in your APN setttings.
https://support.t-mobile.com/docs/DOC-32830
Under APN and data settings, only pay attention to steps 6 and 7. You'll have to go settings->cellular+SIM->SIM settings and then tap to add a new MMS APN.
Follow steps 6 and 7, and then tap the save button. Then apply it and restart your phone. That should work.