To Change "Open Message" and "Close Message":

( Home → Contact Center → Queues → View Queues)

View Queues: This page lets you view all the Queues

Click on a specific queue ID to make the changes.

Edit Queue:  Click on setting and select ‘Open Message’ will be played if the queue is open. ‘Close Message’ will be played if the queue is closed.

And Click on  update to apply the changes.