Hello and welcome to Android Forums. Hopefully I can help you with your problem.
Go into your voicemail and make sure that you have deleted all the voicemails. Then powerdown and do a battery pull. Leave the battery out for several minutes. Install and reboot.
If it's still there, repeat the process. If it is still showing up after you have tried what I've suggested, please make a new post stating the steps your have already taken. Either that or boot into recovery and do a factory reset.
Best of luck. I hope this works for you.
If you have any other questions regarding your device, I invite you to join Android Forums. We have many sections for specific devices which contain a wealth of information.