There is an ICCID, that is usually burned into the eSIM. However, SIM and eSIM are actually a tiny embedded system with a rudimentary Java byte code interpreter

There is an ICCID, that is usually burned into the eSIM. However, SIM and eSIM are actually a tiny embedded system with a rudimentary Java byte code interpreter and you can insert firmware to dynamically swap between the reported ICCID. Usually this is a trick employed by MVNOs to swap between profiles based on the available networks to select the MNO that the MVNO has a more favorable contract with.