Hiya Matt,
you need to add a new user and delete the old one to get rid of the messages, voicemails, call logs, etc. There are a few ways to go about this, I am going to share what I believe is easiest;
To be deleted: Jane
To be added: Bruce
1. Go to Users > Unassigned Ext. > Add unassigned ext > add a user without a license and without a number as the pic below shows.
2. Enable the unassigned ext. for Bruce (Name, Email address, Ext. number)
3.Go to Users > click on Jane > Devices & Numbers > Actions > reassign to > select Bruce
This reassigns the license/phone number from Jane to Bruce.
4. Disable Jane's ext. and then Delete it.
Of course in your case you already have renamed Jane's ext. to Bruce. Which means you just need to create another ext. for Bruce and delete the old Bruce ext.
