[Asterisk-Users] 729 -> 711 failover?

[Matthew Boehm]

Hey guys,
 We currently have 15 Cisco 7940 phones running in SIP mode. All of the
phones can initiate a 729 call and asterisk just does a pass thru. We have
no 729 licenses on the * machine.  We found out that we can't access
voicemail because there is no gsm->729 converter. (duh, no licenses).

 So, we are getting ready to buy some. But, not everybody checks VM at the
same time. So we only want to buy 2 licenses. My question is, lets say 2
people are on VM using the 2 licenses. Will asterisk fail over to g711? If
it wont, why not? Is there a way to make it fail over? I don't think * will
fail over because if I set my cisco phone to "prefered codec = none" and
make a call, it goes 729. But if I call VM * says no can do. Why won't * say
"no can do, let me try the next one"?

sip.conf
---------
allow = g729
allow = ulaw
allow = alaw
allow = gsm


thanks,
matthew