Call waiting needs to be disabled on voicemail ports. In this situation, when called, the Cisco Unity ports see the call waiting tone and drop the connection. The phones then display the Temporary Failure error message as if there was a network disruption.
The problem occurs in new installations of version 3.3(2) Service Pack B (SPB) where call waiting for voicemail ports is set to default rather than to off. If the system setting for call waiting is set to True, call waiting is enabled for voicemail ports.
Normally, busy voicemail ports are configured to roll to the next port to hunt for a free voicemail port. This roll over configuration is achieved by configuring each port to Forward busy to the next port. If call waiting is configured, the call does not roll over to the next voicemail port right away. The call effectively continues to ring until the Call Forward No Answer (CFNA) timer expires. It takes 12 seconds or x seconds (depending on the setting of the CFNA timer) before rolling to the second port on Cisco Unity.
The simplest workaround for this issue is to turn off call waiting system wide by performing these steps:
Go to Service > Service Parameter and select Cisco CallManager Service.
Change the Call Waiting Enable Flag field from True to False.
Restart the Cisco CallManager service.
Note: Turning off call waiting globally does not prevent the feature from being set up on a per line basis. It is still possible to set up call waiting on lines that need it by changing the call waiting drop down from Default to On.
It is also possible to disable call waiting from the voicemail ports by running this script on the Cisco CallManager:
@if "%2x" == "x" goto Usage
echo USE %2 >temp.sql
echo -- disable callwaiting for numplan records associated with voice mail
echo Update NumPlan set tkStatus_CallWaitingEnable = 0 where pkid in >>temp.sql
echo (Select distinct M.fkNumPlan from DeviceNumPlanMap M, Device D >>temp.sql
echo where M.fkDevice = D.pkid and D.tkModel=80) >>temp.sql