Were you able to, or have you already changed the dates? If not, then don't take too much comfort in what the second agent told you because (and I am speculating here), your original routing was AMS-xHKG-CEB where HKG was a "transit point". Now that you want to stop in HKG the ticket needs to be reissued so that it becomes AMS-HKG-CEB.

Good luck and let us know what the outcome is.