You can also just call T-Mobile and ask them to clear your voicemail icon. It's actually a bug on their side that's somehow activated by custom ROMs.
Sent from my Nexus 7 using Tapatalk HD
In the past whenever I have tried to get them to do anything outside of the box they've been useless. I have a "data only" plan with them, so I'm pretty sure their Tier 1 support people will be like "I don't understand!". I may give it a shot if I have the time today, but its been a pretty low priority.