UM Auto Attendant - Hangs up while in use

[stunpals]

I am testing a Exch 2010 auto attendant and when a user is in his/her mailbox, they are suddenly cut off. I haven't timed it yet but its feeling like between 2-3min of use, moving around the menus then all of a sudden cut off?

I have been looking for a timer limit but haven't found anything that seems to be the source.
Any suggestions, would be appreciated.

Exch Standard v14.3 - Build 123.4

 

[stunpals]

I ran a stop watch and after getting logged in to my mailbox, its almost exactly 2min until I am cut off so there is a timer either on Exch UM or my phone system Mitel 3300 that is terminating the call. Anyone have some suggestions on this?