What is the SIM-Swap operation and where has my old SIM gone?

What is the SIM-Swap operation and where has my old SIM gone?

The operation SIM-Swap allows a user to link a new SIM card in Ready to Activate state to an existing endpoint which already has a SIM linked to it.
The operation replaces the ‘old’ SIM with a ‘new’ SIM but keeps all the existing properties of the endpoint (MSISDN, coverage, consumption, balance,…).
The ‘old’ SIM will be removed from the inventory and will no longer be usable. This operation needs to be used carefully but allows a user the possibility to replace a defective or lost SIM for a device.

The existing endpoint can be in Active or Suspended state for the operation SIM-Swap to work. To know more about endpoints and SIM states, check What are the different SIM states and how does SIM life-cycle work?