Not sure if this will be helpful... but you may want to open Messages...press Menu - Settings and in the MMS section ensure that Auto Retrieve is enabled.
Someone else seemed to have a similar issue - http://support.t-mobile.com/message/114251#114251 - no resolution there though.
Yeah, MMS settings were the first things I checked. Auto-Retrieve has been enabled since I got the phone. It will actually "retrieve" the message just fine, but I'll click the little audio icon that appears in the message and it will start playing, with the timebar ALWAYS set to 8 seconds (0:08). This happens even for picture messages; it will just start scrolling through to 0:08. It's fairly annoying...
That is definitely frustrating. You know how when you receive a MMS with a picture, it is always in slideshow format? That could likely be the same for your MMS Voice Text.
How long are these Voice Messages?
Do your videos play straight through as well?
Let us know. We'd like to figure this out for you.
Yes, it is always in slideshow format, including the MMS Voice Text it seems.
The length of these voice messages vary, naturally, but I would say anywhere between 30 and 60 seconds typically. Regardless of the message length, it is ALWAYS truncated after 8 seconds. And, again, the only way to listen to the whole message is to download it, then manually go to it and play it via the audio / music player.
I've never sent / received videos via MMS... the pictures I do receive though do have the timebar play out those 8 seconds. Usually if I'm sent a video, it's via a bit.ly link in an SMS, so I just load it direct over http.