Weird issue here, probably simple to fix. When making internal calls between 4-digit extensions, the history on the phone shows the full external DID. So if you navigate down to that internal call to call them back, it dials the full DID and hits our SIP trunk and comes back in, incurring charges. Every extension at this client has a DID and every person wants their DID to display to the people they call. Is there a way to make the extensions DID not used for internal calls between extensions?
Look at the extension setting in the UCM and see if the CID# is filled in with something other than a blank. If so, change it black to blank and then use the DOD settings for the trunk where you can specify a DID for each extension,