@g4stly, here are some search results: MMS support Telia Sweden? - #18 by irvinewade, Works on AirVoice and How will APN settings work? - #9 by Quarnero.
As above, within serviceproviders.xml all related APN data are written under: <name>T-Mobile</name>. Yet there, within this .xml file, popups this difference: fast.t-Mobile.com vs:
<apn value="fast.t-mobile.com">
<plan type="postpaid"/>
<usage type="internet"/>
<name>T-Mobile LTE</name>
<mmsc>http://mms.msg.eng.t-mobile.com/mms/wapenc</mmsc>
</apn>