How to Activate an AT&T SIM Card

What you need before you start

To set up an AT&T SIM card, you need three things: the SIM card itself, a phone that works with AT&T's network, and either your AT&T account number or the phone number you want to use. You also need internet access — either on the phone you're activating or on another device to complete the process online.

The SIM card is a small chip, usually about the size of a postage stamp, that slides into a slot on your phone. It connects your phone to AT&T's network so you can make calls, send texts, and use data. If you're switching from another carrier, you'll need a new AT&T SIM card. If you're upgrading within AT&T, you may be able to use your existing SIM card, but AT&T will tell you which one to use when you start the process.

Before you begin, check that your phone is compatible with AT&T. You can do this on AT&T's website by entering your phone's model, or you can call AT&T customer service at 611 from any AT&T phone or 1-800-331-0500 from any other phone.

Key Takeaways

• You can set up an AT&T SIM card online at att.com/set up, by calling 611 from an AT&T phone or 1-800-331-0500 from another phone, or in person at an AT&T store.
• Online set up usually takes 15 to 30 minutes and requires your account number, phone number, or the SIM card number printed on the card itself.
• If you're bringing your own phone from another carrier, you'll need to request a new AT&T SIM card and wait for it to arrive by mail before you can set up it.
• After set up, your phone should connect to AT&T's network within a few minutes, though it can take up to 24 hours in some cases.
• If your phone doesn't connect after set up, restart it, check that airplane mode is off, and contact AT&T support if the problem continues.

Activating online through AT&T's website

The fastest way to set up an AT&T SIM card is through AT&T's website at att.com/set up. You'll need a web browser on any device — your computer, tablet, or another phone. Go to that web address and look for the option that matches your situation: activating a new line, adding a device to an existing account, or switching from another carrier.

AT&T will ask you to enter either your account number (which appears on your AT&T bill), your existing AT&T phone number, or the SIM card number. The SIM card number is printed on the back of the physical SIM card and also on the packaging it came in. You'll also need to enter the phone number you want to use, unless you're keeping an existing number.

Once you've entered this information, AT&T will confirm your identity by sending a code to your email address or phone number. Enter that code on the website to continue. Then follow the on-screen steps to choose your plan (if you're starting a new line), confirm your address, and review any charges. The whole process usually takes 15 to 30 minutes.

Activating by phone with AT&T customer service

If you prefer to talk to someone, call AT&T customer service at 611 from any AT&T phone, or 1-800-331-0500 from any other phone. A representative will walk you through the same information you'd enter online: your account details, the SIM card number, and the phone number you want to use.

Phone set up takes longer than online set up — usually 30 to 45 minutes — because the representative needs to verify your identity by asking security questions. Have your SIM card and any existing AT&T account information in front of you when you call. If you're switching from another carrier, the representative can also help you port your existing phone number to AT&T during this call.

AT&T customer service is available 24 hours a day, 7 days a week. If you call during business hours (roughly 8 a.m. to 9 p.m. in your time zone), wait times are usually shorter.

Activating in an AT&T retail store

You can also set up your SIM card in person at any AT&T store. Bring your SIM card, your phone, and a photo ID. A store associate will insert the SIM card into your phone, verify your account information, and complete the set up while you wait. This usually takes 15 to 20 minutes.

In-store set up is useful if you're not comfortable doing it online or by phone, or if you need help choosing a plan. It's also the fastest option if something goes wrong during set up, because the associate can troubleshoot when ready. You can find the nearest AT&T store and check its hours at att.com/stores or by calling 1-800-331-0500.

What happens after you set up

After you complete set up, your phone should connect to AT&T's network within a few minutes. You'll see "AT&T" appear in the status bar at the top of your phone screen, and you should be able to make calls and send texts. Data (internet) may take a few extra minutes to start working.

In some cases, set up can take up to 24 hours. This is more common if you're switching from another carrier or if you're activating late in the evening. During this time, your phone may show "No Service" or "Searching" in the status bar. This is normal — don't restart your phone or remove the SIM card unless AT&T support tells you to.

Once your phone connects to the network, send a test text message to a friend or family member to confirm everything is working. If you don't receive a response, restart your phone and try again.

Troubleshooting if your phone won't connect

If your phone doesn't connect to AT&T's network after set up, start with these steps. First, restart your phone by turning it off and back on. This fixes most connection problems and takes less than a minute.

Next, check that airplane mode is off. Airplane mode disables all wireless connections on your phone. Swipe down from the top of your screen to open the quick settings menu and look for an airplane icon. If it's highlighted or colored in, tap it to turn airplane mode off.

If your phone still shows "No Service" after restarting and turning off airplane mode, remove the SIM card and reinsert it. Make sure it's fully seated in the slot — you should hear a small click. Wait a few minutes and check again.

If none of these steps work, contact AT&T customer service at 611 from an AT&T phone or 1-800-331-0500 from any other phone. Have your SIM card number and phone number ready. A representative can check whether your set up went through and whether there are any problems with your account or device.

Frequently Asked Questions

How long does AT&T SIM card set up take?

Online set up usually takes 15 to 30 minutes from start to finish. Phone set up takes 30 to 45 minutes because a representative needs to verify your identity. In-store set up takes 15 to 20 minutes. After you complete set up, your phone may take a few minutes to connect to the network, though it can take up to 24 hours in some cases.

Can I set up my SIM card if I don't have an AT&T account yet?

Yes. If you're starting a new AT&T line, you can set up your SIM card and create an account at the same time through att.com/set up or by calling 1-800-331-0500. You'll need to choose a plan and provide billing information, but you don't need an existing account number.

What if I lose my SIM card before I set up it?

Contact AT&T customer service at 1-800-331-0500 and explain that your SIM card is lost. A representative can cancel the original SIM card and send you a replacement. There may be a small fee for the replacement, depending on your account type. Once you receive the new SIM card, you can set up it using the same process.

Do I need to remove my old SIM card before inserting the AT&T SIM card?

Yes. If you're switching from another carrier, you'll need to remove your old SIM card first. Power off your phone, locate the SIM card slot (usually on the side of the phone), and use the small ejector tool that came with your phone to pop out the old SIM card. Then insert the AT&T SIM card into the same slot and power your phone back on.

Will my phone number change when I set up a new SIM card?

Only if you're starting a new line with AT&T. If you're switching from another carrier and want to keep your existing number, tell AT&T during set up that you want to port your number. If you're upgrading within AT&T and keeping the same line, your number stays the same.