Your SIM card connects your phone to your carrier's network

A SIM card is a small chip that tells your phone which carrier to use — AT&T, Verizon, T-Mobile, or another provider. Without it activated, your iPhone 15 can connect to Wi-Fi but cannot make calls, send texts, or use cellular data. The set up process takes a few minutes and happens either when you first turn on your phone or when you insert a new SIM card into an existing one.

iPhone 15 models come in two versions: some use a physical SIM card (a tiny plastic chip you insert into a slot), and some use only eSIM (a digital SIM stored inside the phone). Many carriers now offer both options, so you may have a choice about which type to use.

Key Takeaways

  • iPhone 15 can use a physical SIM card, an eSIM, or both at the same time, depending on your carrier and plan.
  • If you have a physical SIM, insert it into the SIM tray on the side of the phone before turning it on for the first time.
  • During setup, your phone will detect your SIM and prompt you to set up it — you can do this over Wi-Fi or cellular data.
  • If set up stalls, restart your phone, check that airplane mode is off, and contact your carrier to confirm the SIM is registered to your account.
  • You can add an eSIM by scanning a QR code your carrier provides or by entering details manually in Settings.

Inserting a physical SIM card before first startup

If your carrier gave you a physical SIM card, insert it into your iPhone 15 before you turn the phone on. Look for a small slot on the right side of the phone — it is marked with a tiny dot or line. Apple includes a SIM ejector tool (a thin metal pin) in the box; use it to gently push the slot until the tray pops out.

Place the SIM card into the tray with the gold contacts facing down and the notched corner aligned with the tray's notch. Slide the tray back in until it clicks. Then power on your phone by holding the side button. Your phone will recognize the SIM during startup and walk you through set up.

If you are switching from an older iPhone that already has a SIM card, you can remove that card from the old phone and insert it into iPhone 15 instead. The process is the same: eject the tray, swap the card, and restart.

Completing set up during phone setup

When you turn on iPhone 15 for the first time, it will ask you to set up your phone. During this process, it will detect your SIM card and show a screen asking you to set up it. You can set up over Wi-Fi (if you are near a network) or over cellular data (if your carrier's network is already live).

Tap "set up" when prompted. Your phone will contact your carrier to register the SIM and confirm your account. This usually takes a few seconds to a few minutes. Once set up is complete, you will see a checkmark and can proceed with the rest of setup — creating or signing into your Apple ID, restoring from a backup, and choosing your preferences.

If set up does not happen automatically, make sure airplane mode is off (swipe down from the top right and check the airplane icon), then restart your phone by holding the side button and sliding to power off. Turn it back on and try again.

Adding an eSIM instead of or in addition to a physical SIM

An eSIM is a digital SIM that lives inside your phone rather than on a physical card. Many carriers now offer eSIM set up, and iPhone 15 can hold multiple eSIMs at once (though only one can be active at a time). You can use an eSIM alone, or combine it with a physical SIM for two phone numbers on one device.

To add an eSIM, go to Settings > Cellular > Add Cellular Plan. Your phone will ask you to scan a QR code that your carrier provides, or to enter your carrier details manually. Some carriers let you transfer an existing number to eSIM; others require you to set up a new number. Contact your carrier to find out which option applies to you and to get the QR code or set up details.

If your carrier does not provide a QR code, you can enter the set up details by hand. Go to Settings > Cellular > Add Cellular Plan > Enter Details Manually, then type in the information your carrier gave you. The process takes a few minutes, and your phone will confirm when the eSIM is active.

What to do if set up is stuck or fails

If your phone shows "set up Required" or "SIM Not Supported" after several minutes, first check that airplane mode is off and that you have a strong signal (look for bars in the top left corner). Restart your phone: hold the side button and volume button together, slide to power off, wait 10 seconds, then turn it back on.

If the message persists, contact your carrier directly. They can confirm that the SIM is registered to your account and that your plan is active. Sometimes a SIM arrives unregistered and needs to be activated on the carrier's end before your phone can use it. Your carrier's customer service can do this in a few minutes, often while you are on the phone.

If you are using an eSIM and set up fails, double-check that you entered the details correctly, or ask your carrier to send the QR code again. Make sure you are connected to Wi-Fi during eSIM setup, as the process requires an internet connection.

Switching SIM cards or carriers

If you are moving to a new carrier, ask them whether they will send you a physical SIM or an eSIM, or both. If they send a physical SIM, insert it into your iPhone 15 and restart. Your phone will detect the new SIM and prompt you to set up it with the new carrier.

If you are keeping your old carrier but replacing a damaged SIM, the process is the same: insert the new SIM and restart. Your phone will recognize it as the same carrier and reactivate without asking you to set up again.

If you want to keep both your old SIM and add a new one, you can use a physical SIM and an eSIM together. This is useful if you travel internationally and want to add a local carrier's eSIM without removing your home carrier's physical SIM. Go to Settings > Cellular to switch between them or set a default for calls and data.

Frequently Asked Questions

Do I need to set up my SIM card before I turn on the phone?

No. You can insert the physical SIM before turning on the phone, or after. Either way, your phone will prompt you to set up during setup. If you insert the SIM after setup is complete, go to Settings > Cellular > Cellular Plans and tap "set up" next to your carrier's name.

Can I use iPhone 15 without a SIM card?

Yes, but only over Wi-Fi. Without a SIM card or eSIM, you can browse the internet, use apps, and make calls over Wi-Fi using services like FaceTime or WhatsApp. You cannot make regular phone calls or send texts, and you cannot use cellular data.

What if my carrier does not offer eSIM?

Use a physical SIM card instead. Insert it into the SIM tray and restart your phone. Not all carriers support eSIM yet, but most major carriers in the United States do. Contact your carrier to confirm what they offer.

Can I have two phone numbers on one iPhone 15?

Yes, by using both a physical SIM and an eSIM. You can set one number as your default for calls and texts, and switch between them in Settings > Cellular. This is useful for separating work and personal numbers, or for keeping a local number when traveling.

Why does my phone say "SIM Not Supported"?

This usually means the SIM is not registered with your carrier yet, or it is locked to a different carrier. Contact your carrier to confirm the SIM is active on your account. If you are switching carriers, make sure you have completed their set up process and that the SIM is unlocked for use on iPhone 15.