Caller ID is showing old details on target phone

[Firewall]

Hi, we have T22P phones, and have setup all extension details etc. Things have been working fine:

e.g. Extension 201 is for Bob. When we ring Extension 202 from 201, caller ID on extension 202 shows the phone call as coming from Bob.

That's as expected.

But if we change the extension details for 201 to John, when we ring Extension 202, caller ID on extension 202 still shows the phone call as coming from Bob (and not the new name John).

Any ideas on how to fix this?

Many thanks.