How can I disable voicemail notifications?

I have a prepaid T-Mobile line that I use for development purposes only. I do not really use it for calls. However, some 800-number company has been calling me constantly (which I have already added to a "block" contact which directs all calls to voicemail via Contact app menu option). However, they leave voice mails which creates this notification on my phone: Click the image for larger variance But I cannot swipe away this notification. It is a constant and persistent notification. Is there a way I can either: 1. Never show voicemail notifications (without having to call T-Mobile and disable my voicemail box) 2. Swipe to remove the notification or hide the notification (via an app or similar?) I am rooted on a stock Nexus 5. I would have just used Google Voice as my voice mail box but apparently T-Mobile prepaid lines cannot have call forwarding so I can not use that option.