Could you update more detail about your issuse.

A common problem in the voice network is when no dial tone is heard from a voice port in the off-hook condition. This could be related to configuration issues, a hardware problem, a Digital Signal Processor (DSP) problem, or a bug in Cisco IOS? software. A voice port that is configured with connection trunk does not provide dial tone. A faulty network module or Foreign Exchange Station (FXS) card may cause silence or no dial tone in a voice port.

Troubleshooting No Dial Tone Issues:

http://www.cisco.com/en/US/tech/tk1077/technologies_tech_note09186a00800a4795.shtml