Sim card
To activate a new unlocked SE iPhone - how do I get a SIM card?
Question marked as
Top-ranking reply
Do you still have a SIM card from your 'old' iPhone?
If so, you can use that SIM card and keep the same phone number & the same carrier.
That is also handy then you don't have to change anything, you use the same number.
If the SIM format is different, visit or contact your carrier and request a replacement SIM card, normally it is free.
If you don't have a SIM card, look for / visit a carrier, take a subscription, postpaid or prepaid card.
Check whether the SIM card is suitable for your iPhone.