My old iPhone was shipped back with the Sim card. What can I expect to happen to the Sim card?
What happens to a Sim card that was included in a return of an iPhone?
If you’ve already updated your cellular plan info with the carrier (either cancelled or transferred it), then the SIM card is now electronic waste. Which means it’ll get recycled. (There are various reasons why eSIMs can be preferable, and this is one.)