Inbound CID showing unknown

I am using Asterisk v1.4.2 FreePBX v2.5.0.1 and trixbox v2.6.1 until recently all inbound CID from the PSTN were showing up on all my IP phones, now they all say ‘Unknown’. I think something has changed but I don’t know where to check the CID configuration. Is it
possible that my Telco stopped sending CID?

Yes it is. Do you have a way of testing the Telco lines directly?

I found out that my Telco is sending key line instead of DID. Once that is changed I will be able to set up my DIDs and get CID.