Let's start with what version of Unity are you working with? Just to get clarification. Next, what are you experiencing? It should not take any length of time for a new number to take affect in Message notification. As long as you change the number, enable it and safe the changes, it should take affect immediately.
As for the number of rings, it is set in Unity. On the bottom of the Message Notification page, there are setting for the number of rings before haning up. Are you setting this to one and seeing the notification phone ring more than what is set? Please elaborate.
Jeff Schlesser
Unified Voice Technical Lead
San Jose TAC