I thought I would post the resolution to this issue that I had. When I installed this system we programmed several phones with the Caller ID block feature for making collections calls, etc. One thing I did not mention was that the CLEC had recently converted them from a pure PRI to a SIP service with a PRI handoff. This SIP service did not allow anonymous Caller ID. The reception desk had the Caller ID Block turned on, which attempted to make the call anonymous, and the CLEC was denying the processing of the call. I removed the CID Block button from all phones.