Purpose and preparation
Use the official appointment system for the relevant ICA service. Have the application/approval or collection notice available to choose the correct task and required attendance.
Choose the correct operation
Changing/cancelling an appointment does not cancel or renew the underlying pass. Observe the document/attendance deadline in the notice even when rescheduling.
Official ICA source
Written independently from ICA’s English original. The linked source supplies the complete document and subsequent updates.