Hello! Are you using visual voicemail? If not, call voicemail and make sure it is not indicating that you still have an unheard message. I know you said that you tried everything, but I don't know what that entails, so make sure you reboot your device if you haven't already. If you are using an app, you can try uninstalling and reinstalling. If none of that works, you should check with your carrier and see if they can help. Good luck!