Ever since I upgraded to WP 8.1 my voicemail alert has been the same as my ringtone how do you change that. I cannot seem to find a setting for voicemail. Ugh.
I found this to work on an AT&T Nokia 920. I was just recently updated to 8.1.
Go to "Settings", then "ringtones+sounds". In this screen you can set the ringtone for when someone calls you, and the sound for when you have a Reminder.
For your voicemail ringtone, or voicemail notification sound. Go to "Settings", then "notifications+actions". Next, scroll down to "Phone" and tap it. In this screen you you have a menu box to choose a Notification sound. This is the sound that will occur when you receive a voicemail.
They are not very clear that this is for voicemail to say the least.