This guide provides more information on why if you delete an agent is still showing up on all Analytics.
ContactNow, Agents, Analytics
If you have removed one or more agents, but using the reports you can still see the analytics for them and wondering why, there is no need to worry. For auditing purposes, they will continue to appear and by doing so you will always have records on how money was spent on your contact centre account.
Currently, a workaround we are able to provide is to filter the data by agents, as seen in the following image: