[Blind-sysadmins] Text to speech for incoming call announcement on Cisco VoIP Phone CP8841

I'm using a Cisco VoIP phone model CP8841. We've enabled the TTS functionality, and it's working well other than that when I receive a call from an outside unknown caller, the phone announces "unknown caller" and does not provide the caller's number. Has anyone encountered this and perhaps found a workaround? Chris