Rename the 'To voicemail' button when there's an incoming call when voicemail is disabled.

At the moment, when voicemail has been disabled from permissions, the 'To voicemail' is still an option when voicemail has been disabled. When pressed, it plays an announcement and disconnects as it should. The 'To voicemail' button can be quite misleading for users. The button should be renamed to 'Reject' or 'Decline' when voicemail has been disabled.