SIM Cards: Everything you need to know

SIM cards and mobile phones have gone together since mobile phones first became a thing. Yet there are still plenty of questions people have around SIM cards, including how they can get them working, how they work, and what they can exactly do. But don’t worry, we’re here to answer all your SIM card-related questions.

Jump to:

What does a SIM card do?

A SIM card (or ‘Subscriber Identity Module’) is a small chip that stores your phone number and gives you the ability to use your phone for calling, sending texts and using data on the go. SIM cards come in different sizes depending on the phone type and are used to authenticate your access to a mobile network (in Australia, this would be a network operated by Telstra, Optus or Vodafone).

When you call somebody, send a text message, or use the internet away from a WiFi signal, it’s because of your SIM card that you’re able to do this. Without a SIM card you wouldn’t be able to do these things, and ultimately your phone would be very limited in its capabilities.

Does my phone need a SIM card to work?

You will need a SIM card in your phone if you want to use it for phone calls, texting or using mobile data. Without a SIM card, you also won’t have a reachable phone number. While ‘Simless’ phones (or eSIMs) are starting to enter the market, most phones will still require you to use a SIM card, which can be inserted into your phone through a special port on the side.

Not having a SIM card doesn’t mean the phone won’t work. As a piece of technology, the phone will still be functional, turn on and be usable for browsing on a WiFi network – it just won’t be able to call, receive calls, text or use mobile data.

A SIM Card being inserted into a phone

Do I need a different SIM for different telcos?

You’ll need to be issued a new SIM card if you switch to a different telco. You can bring your phone number with you if you arrange for a number transfer with your selected telco, but you will need a new SIM card if you’re changing provider.

If you’re changing your mobile plan from your same telco provider, you won’t need a new SIM. This change can all be done provided that you have your SIM identification number on hand.

What are the SIM card sizes?

Sim cards come in three different sizes which cater for the size of the phone you’ll be putting them in. None of the SIM card sizes are better than the others and they’ll all function the same way. It just comes down to what SIM card will fit into your phone. Typically when you get a new SIM card, you’ll be able to pop the SIM card out into the size that suits your phone.The three types of physical SIM cards - Standard, Micro and Nano (Left to right)

The Standard SIM

This SIM card fits into older-model phones such as the iPhone 3GS, Huawei Y3 and the Samsung Galaxy Ace. It’s very rare that you’ll see a phone fit this size, and unlikely that we’ll see it come back.

The Micro SIM

The micro SIM size fits into phones that are not as old as those that use standard SIM, but typically haven’t come out in the past year. The iPhone 4S, Motorola Moto G4 Plus and Samsung Galaxy J3 each use a micro SIM. It’s unlikely that you’ll see a new phone with this SIM size too.

The Nano SIM

The Nano SIM is the most common SIM card type for new phone releases, and it’s also the smallest. You’ll be hard pressed finding a new phone that doesn’t use a Nano SIM, with every new Samsung, iPhone and Google phone using them for the past four years.

Alternatively, we’re starting to see phones enter the market as ‘simless’ phones – phones that don’t require you to insert a SIM card. These are quite new and are far from being the expected standard. Some of these are the iPhone 11, the Samsung Galaxy S20, the Huawei P30 Pro and the Samsung Galaxy Note 10.

Note that these phones are also all capable of using nano SIMs, but if you so wish, you can use them SIM-free.

How do I activate a SIM card?

Here’s some easy steps to follow when activating your new SIM card:

  • Remove the SIM card slot from your phone

This is a small slot on the side with a tiny hole, which can be opened by inserting something thin into the hole. New phones will come with a pin to make this easy, but alternatively you can use a thin paperclip or a thin-bristled and sturdy brush.

  • Place your SIM in the slot, and put it back in your phone

You may have to rotate the SIM or the slot, but a small chip in the corner of the box-like shape will designate where the SIM needs to go.

  • Insert the SIM slot back into your phone

Be careful not to drop your SIM card as you’re sliding the SIM slot back into the device.

A SIM being inserted into a phone

  • Be ready to activate your SIM card

Depending on the telco provider, this step might vary. You may receive some paperwork with the sleeve your SIM card came in, which will have an activation key on it, or you could receive a text shortly after inserting the SIM.

  • Follow the steps that your mobile service provider is prompting you to do

Have a valid ID on you (such as a credit card, passport or drivers licence) so that you can be verified. You’ll likely need to activate the SIM on your provider’s website, so be ready to type in information and set up an account.

  • Your new SIM should be ready to use now

Allow up to four hours for activation time. Provided every action was followed in step five, you should have a new SIM ready with no issues.

Alternatively you can check out our article on this here.

Why is my SIM card not working?

If your SIM card isn’t working, don’t worry – there’s always a fix. See some of the possible issues below.

  • Try waiting up to four hours for your service to be activated
  • Check if there’s any scratches on your SIM card
  • Your SIM slot could use some cleaning
  • Your phone could need to reboot
  • The SIM card slot could be damaged, or your phone software could be damaged

The first four steps are quite easy to fix. If you’ve just activated your SIM card, it could take a while before you can use it. Wait up to four hours and then try something else.

If you suspect your SIM card is damaged, you could contact your telco and order a new one. Allow for shipping.

If you suspect your SIM card slot is dirty, remove it from your phone and clean it with a cleaning cloth and Isopropyl, so you don’t damage the technology.

Try rebooting your phone, or switching it on and off airplane mode.

If you suspect your phone’s software could be corrupted or that your SIM card slot is damaged, you might need to order a new phone. If it’s still within warranty, you could claim it as damaged, and send it off to be repaired. If it’s not within warranty, you could consider paying to have it repaired, by a third party or the original manufacturer.

Should I get a prepaid or postpaid SIM?

SIM cards come with two payment options, prepaid and postpaid. Prepaid plans are where you pay for your call, text and data usage upfront, and are typically better for managing your data and spending. Postpaid plans are where you’re billed for your usage at the end of each month, meaning you could rack up a bigger bill than expected.

We’ve gathered a bunch of great prepaid and postpaid SIM plans below, so you can decide which ones are the best for you and your lifestyle.

Here is a selection of postpaid plans from Canstar Blue’s database with a minimum of 10GB of data, listed in order of standard cost, lowest to highest, then by data allowance, largest to smallest. Use Canstar Blue’s phone plan comparison tool to see a wide range of plans on offer from mobile providers. This table includes products with links to referral partners.

Here is a selection of prepaid plans from Canstar Blue’s database with a minimum of 10GB of data, listed in order of standard cost, lowest to highest, then by data allowance, largest to smallest. Use our comparison tool to see a wide range of plans from other providers. This table includes products with links to referral partners.

Share this article