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How To Activate A SIM Card: A Step-By-Step Tutorial

close up of a sim card

Your SIM card, also known as your subscriber identity module, is the piece of hardware that gives your phone its personalized identity. The SIM card connects your phone to your carrier and basically allows it to function as a phone.

SIM cards are a piece of technology that modern-day phones cannot go without, and it is important that we make sure they are functioning correctly. Without a SIM card, our phones are almost useless, so it is vital that we understand their value and how they work.

While technology continues to advance and make our phones more and more complex, without a SIM card they are still nothing but miniature computers at best. Given how important it is to make sure your SIM card is working right, here is how you make sure yours is properly activated.

What Is a SIM card?

A SIM card is basically the brain of your phone, allowing you to maintain a personal phone number that is tied to a specific network. The features of your phone that have to do with calling and texting require you to have an individualized SIM card. All phones have some kind of SIM card, whether they be an old-school flip phone or cutting-edge smartphone.

A phone isn’t dead without a SIM card, especially not modern phones. Many phones have internet and application capabilities that act independently of your SIM card.

However, at that point, the phone is just a miniature computer with no capacity to connect to a mobile network. Just like how your laptop is not explicitly tied to your identity through internal hardware, without a SIM card your phone is just a generic device without a phone number.

There are a couple of different types of SIM cards, namely GSM (Global System for Mobile communication) and CDMA (Code Division Multiple Access). GSM technology involves a physical SIM card that you can remove and put in a new phone, retaining your existing mobile identity despite the device change.

CDMA involves having a virtual electronic serial number that is tied to the phone. This is much more difficult to change as the phone is explicitly tied to the carrier directly.

Traditional SIM Cards

Traditional SIM cards are a card inside of your phone that store personal info that makes that phone unique. It connects you to your network, and oftentimes it will also store your contacts, making a switch from one cell phone to the next relatively painless.

When switching between carriers, you cannot keep your original SIM card. However, you can work with your new carrier to try and have your phone number preserved during the transition so that you can continue using it. Many phones today also offer cloud storage capabilities that let you save your phone’s info online to be immediately copied onto your new phone at your leisure.

What Is an eSIM?

Contrary to what you may think, an eSIM is still a physical piece of hardware; the ‘e’ actually stands for ‘embedded.’ eSIMs are writable, meaning the information on them can be altered. This allows you to switch between carriers without having to replace any hardware. All you have to do is connect to the Wifi and complete the upload or rewrite process online.

This is necessary because eSIM cards are not removable in the first place. This could be a knock against them for people who prefer to have the option of removing them. This technology does allow for dual SIM phones with two phone numbers to exist.

As of this time, many phones have not converted to eSIM, but it is a quickly growing technology that is used in some of the best devices on the market.

How To Activate Your SIM Card

While activating your SIM card isn’t a complicated process, it is slightly different for each carrier because most companies have you activate it through their network. Here is the process for activating your SIM card on each of the big three telecommunications networks.


  1. Log into your T-Mobile account.
  2. Select the line of service that you want the change to occur on.
  3. Complete the security verification process.
  4. Select either SIM or eSIM, depending on what type of SIM card you are attempting to transition.
  5. Follow the prompts and enter either your ICCID or EID number to complete the switch.

T-Mobile also allows you to purchase a SIM card directly from the carrier if that is the route you want to go down. If you want to change an eSIM you have to make sure you are connected to Wifi first.


In order to activate your SIM card through Verizon, do the following:

  1. Access your My Verizon account.
  2. Select the ‘Activate or Switch Device’ page.
  3. Follow the prompts to activate your device.

Regardless of your carrier, Verizon emphasizes the importance of making sure that you identify whether or not the two phones you are transitioning between are compatible when it comes to the SIM card. Not all SIM cards are compatible with all phones, so check in before making a commitment.


The first thing AT&T recommends is that you place a test call to see whether or not your phone came pre-activated. If not, these are the steps for activating your SIM card:

  1. Go to
  2. Select ‘Activate your device.’
  3. Follow the prompts to complete activation.

If this doesn’t work for AT&T or any of the other carriers listed, you can always look for a physical branch of the carrier and try to get the process done in person. However, if you have consistent internet access then the process is so simple that it should be done in minutes.

The Bottom Line

A SIM card is what makes your phone your phone, and without it, you won’t have a personalized phone number or access to a cell carrier. Activating your SIM card is a relatively easy thing to do, but it is important to make sure you do it right, and the process varies by carrier.

When shopping for a new cell phone, it's important to pay attention to whether the model you're considering uses a traditional SIM card, a dual SIM or an eSIM, as this will impact how to activate your SIM. To find the best phone deals from top wireless providers that you qualify for, try our free, unbiased Phone Deal Finder below.

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