I was just reading the following Article and wanted to add few things that helped me solve my issue:
#11 : SIP 9971 phone unable to complete PSTN calls
*** bearer-cap speech ***
This simple command also fixed an issue I had with Jabber clients calling from Softphone mode to cellphones, and they were getting straight to the voice mail of that particular cellphone.
At first it looks like a simple issue with the phone company, but then you start re-thinking it because it happens with every cellphone you make and with every SIP device you have connected to CUCM.
A quick debug isdn q931 helps determine the issue:
A normal call will have:
Bearer Capability i = 0x8090A2
A failed call wil have the following:
Bearer Capability i = 0x8890
And last while the call is disconnecting you will see the following:
1515501: *Apr 17 19:00:53.002: ISDN Se0/0/0:23 Q931: RX <- DISCONNECT pd = 8 callref = 0xB68D
Cause i = 0x83C1 – Bearer capability not implemented
I was able to take a look at the Bearer codes in the following page:
http://www.cisco.com/c/en/us/support/docs/voice-unified-communications/unified-communications-manager-callmanager/67141-ip-phone-fail-vta-bearer.html
About the Author:
Andres Sarmiento, CCIE # 53520 (Collaboration)
With more than 13 years of experience, Andres is specialized in the Unified Communications and Collaboration technologies. Consulted for several companies in South Florida, also Financial Institutions on behalf of Cisco Systems. Andres has been involved in high-profile implementations including Cisco technologies; such as Data Center, UC & Collaboration, Contact Center Express, Routing & Switching, Security and Hosted IPT Service provider infrastructures.