We don't have the original box anymore, so is there any way we can obtain the IMEI number, so that all providers can blacklist this phone?  It wasn't purchased by us, so don't have receipts etc.

Is there any network magic that identifies the IMEI number of the phone as it traverses the 2degrees network?

Phone was quickly turned off by the looks, so find-my-phone is no use.  We have suspended the number, so the account can't be used, but want to kill off the hardware as well.

On a related note, we swapped this number over to a micro-SIM when moving from the old iPhone to this one.  Went to SIM-swap back to the original SIM to fire the old phone back up, but I need to buy a new blank SIM to do this.  Why can't we just re-use the previous SIM?