When an off-net caller (user A) dials in through the PRI to a DID that is programmed for Mobile Connect the CLID on the receiver's phone (user B) appears correctly. This call shows the correct 10-digit CLID of the original caller A.
When an on-net caller (caller C) who has a 4-digit internal extension and is in another location from caller B 4-digit dials to caller B ,the CLID on caller B's cell phone shows up incorrectly.
Here's an example:
Caller A's CLID is 212-555-1212 and dials caller B at 847-222-3333 = caller B's cell phone displays correctly as 212-555-1212.
Caller C is in a different city than caller B so their area codes and prefixes are different. Caller C dials caller B's 4-digit internal extension of 3333. On caller B's mobile phone he sees 847-222-8888 which is caller B's area code and prefix plus caller C's last 4 digits. Instead, caller C's CLID should show up as 321-777-8888.