When a user places a call to a cellular phone and receives the message "please wait while we locate the subscriber," the cellular phone drops the call intermittently. Non-cellular phone calls are fine. The public switched telephone network (PSTN) connection is via a Cisco Catalyst 4000 Access Gateway Module (AGM) blade and a PRI.
The problem is related to the PRI not receiving an updated call_proceeding message within the timeout period.
Resolve this issue by adjusting the timeout on the gateway for the ISDN t310 timer.
Set the timer to a high value, such as 60000. This value makes the timeout 60 seconds which should be long enough for any network. The timer is found under the serial interface configuration on a Cisco AS5300, 2600, 3600, 3700, and other IOS gateways such as the Catalyst 4000 AGM.