Why does the callback function fail when pressing the “RD” button on the phone directly (the screen displays “unfound”)?

It’s because that the callee replaces its caller ID with English letters. When the “RD” button is pressed to call back, the phone will call the callee’s “Caller ID” directly. But MyPBX system recognizes the callee only by “Extension number ” rather than “Caller ID”. So the phone screen would displays