The problem actually seems to be a data connection issue in my experience. I have been having problems recently with messages and phone calls not coming into my phone (system issue) and noticed that my voicemail indicator would not change it's state letting me know I had listened to all my voicemails already. What T-Mobile ended up having to do (to solve my other issue) was remove my phone from the system, reset the account (all connections in their end), and readd me to the network afterwards. Once I was able to get data and voice calls the voicemail indicator reset itself. I have had this happen 3 times in the past two weeks but the last time was when they reset everything on their end. We will see if it stays.