What’s a SIM card and what does it do?

To get the best cell phone coverage, you need a SIM card. But what exactly is a SIM card? A woman we know was certain it had something to with The Sims, the video game her kids used to play. It was kind of funny. But still, we had to set her straight.

In the wireless world, SIM stands for subscriber identity module and a SIM card is a small circuit board that enables your cell phone to connect with your wireless carrier’s network. That makes it a pretty important feature of your phone.

What are the functions of a SIM card?

Your SIM card stores the information that enables your wireless provider to recognize it. Otherwise you couldn’t text anyone or post anything. Your phone number is stored on your SIM card along with what are called “authorization keys.” These give your phone authorization to access the data, texting, and other services provided by your cell phone plan. Without a SIM card, your phone could not access and utilize your wireless provider’s network. That would not be a good thing!

Where is the SIM card located?

The SIM card is located on either the right or left side of your phone. To access it, look for what appears to be a tiny hole or indentation. (If your phone is in a phone case, remember to pop it out.) To get to your SIM card you can use what’s called a SIM ejector tool or – why give yourself a headache? – a paper clip. Press the clip into the small hole and the SIM tray panel will pop open.

What is a dual SIM?

A dual SIM phone means you can put two SIM cards into one phone. This lets you manage two phone numbers, each with their own SIM card, on the same device. This is a neat feature if you want or need to have two phone numbers say, one for business use and one for personal use, and really don’t want to lug around two devices. You can make calls from either number, and receive calls to either number. When making calls, your device will ask you which SIM card you want to use.

SIM cards aren’t “attached” to one phone. Except when they are

In general, you can remove your SIM card and put it in a new phone. You can even take someone else’s SIM card and put it in your phone. But sometimes, certain wireless carriers don’t permit this easy switching. And that’s why it’s important that we discuss locked and unlocked phones.

About unlocked and locked phones

An unlocked phone is a phone that’s not associated with a particular wireless carrier. One of the big benefits of this is that you can switch providers anytime you want – like when you find a plan that gives you all the bells and whistles the pricey wireless companies promise at half the price. (But we’ll get to that in a minute.)

On the other hand, a locked phone is a device that’s tied to a carrier like AT&T, T-Mobile, or Verizon. These carriers “lock” your device to their network to prevent you from using it on another one. (Like the better, less expensive one we just alluded to.)

How can I tell if my phone is locked or unlocked?

If you bought your phone from, say, AT&T, Verizon, or T-Mobile, and you have a monthly contract with them, your phone is most likely locked to their network. That’s just how they roll. If you bought your phone at Best Buy or at an Apple store or on Amazon, or someplace else entirely, it is most likely unlocked. The key phrase there is “most likely.” You can’t be certain until you check.

How to determine if your phone is locked or unlocked


Check your settings: iPhone

One way to tell if your iPhone is unlocked is to go to Settings, then Cellular, then Cellular Data. If the words “Cellular Data Network” appear, it’s most likely – but not definitely – that your phone is unlocked. The pricey wireless providers really make you jump through hoops.

Check your settings: Android

One way to tell if your Android phone is unlocked is to go to Settings, then Connections, then Mobile Networks, then Network Operators. While in Network Operators, click on “search now.” If a variety of wireless carries names pop up, it’s most likely – but not definitely – that your phone is unlocked. Once again, pricey wireless providers will work your last nerve.


Contact your wireless provider

You can call the customer service department for your carrier and ask them to see if your phone is locked. You can also request that they unlock it. If you’d prefer to talk with someone in person, you can always visit one of your carrier’s stores and do the same thing. For those who are more tech savvy, it’s worth checking out your provider’s website to see if it offers information on how to unlock your phone. It’s important to note that, once you’ve requested your phone be unlocked, it can take your carrier 48 to 72 hours to do so. After that time has elapsed, call them to confirm that they have indeed unlocked your phone. You don’t want them conveniently – or inconveniently, for you – forgetting to do so.

Customer Service Numbers for:

AT&T: 1-800-331-0500

Verizon: 1-800-922-0204

T-Mobile: 1-877-453-1304

Cricket Wireless: 1-800-274-2538

Mint Mobile: 1-800-683-7392.

Straight Talk: 1-877-430-2355

Boost Mobile: 1-833-502-6678


Try switching SIM cards
Another way to determine if your phone is locked or unlocked is by switching out the SIM card. Simply borrow one from a family member or friend whose service is provided by a carrier different from yours.  Then test it out in this manner:

  1. Shut down your phone.
  2. Remove it from the case, if it’s in one, and then remove your SIM card.
  3. Put in the SIM card you borrowed.
  4. Close the SIM tray.
  5. Now, turn your phone back on.

If you get a message requesting a code to unlock the SIM card, your phone is locked to your network provider. If you can use your phone like you always do, make and receive calls, send and receive text messages, your phone is unlocked.

How does a SIM card function when I travel outside of the United States?

It functions just the way we described it earlier: it allows your wireless provider to recognize your phone number so you can utilize your wireless provider’s network.

However, before traveling out of the United States, check into the roaming fees your provider charges. They can be some pretty big fees which means you might want to obtain a SIM card once you’ve arrived at your destination. Doing so means you’ll pay the same prices as the local citizens do.

It sounds like an unlocked phone and the ability to switch out my SIM card is the way to go. But what are all the benefits to it?

  1. If you want to switch service providers for any reason at any time, it’s a whole lot easier – not to mention a whole lot less expensive – to unlock your phone than to go buy a new one. Think about it. Spend a few minutes getting your current device unlocked or plunk down $600 on a new one? We think spending a few minutes is the way to go and we think you’ll agree.
  2. If you would like to sell your device there’s no wondering or hoping that the purchaser’s provider is compatible. When your device is unlocked, anyone can buy it and start using it immediately. No hassles. Now down time. An unlocked phone makes that transaction nice and easy.
  3. When traveling internationally or just making international calls, an unlocked phone allows you to use local SIM cards rather than paying the super high roaming fees many providers charge. If you make a lots of international calls on a regular basis, you can save hundreds of dollars each year.

In short, the greatest benefit to unlocking your phone is the ability to change carriers because… you’re not getting great coverage…. or your cell signal is spotty… or because you discovered what may be the best unlimited plan with such tremendous savings for yourself and your family that it would be crazy not to switch.

Discover unbeatable savings with H2O Wireless

Now that you’ve learned the ins and outs of SIM cards and the importance of having an unlocked phone, you’ve got the freedom to say “Yes” to unlimited talk, text, and 2GB of data for just $20 a month. That’s right. With H2O Wireless’ Unlimited Plans, you’ve got the freedom to pick the plan that works best for your lifestyle. For as little as $20 month – or $18 a month if you enroll in auto pay – you can enjoy the same 5G network – America’s most reliable network – as those overpriced wireless companies. You know – Verizon, AT&T, and T-Mobile – the folks who lock your phone and tether you to their plans. Today’s 5G network provides the best cell coverage at significantly greater speed and is far more flexible, reliable, and secure than any network before it. (Take that, 3G!)

What does the 5G network and its incredible speed mean to you? It means not having to worry about whether or not you’ll miss the next episode of Ozark, Selling Sunset, or Bridgerton – you won’t, or connect with your best friend before he or she leaves for a 10 day white water rafting trip down the Colorado River – you will.

Plus, with H2O Wireless, you can bring your phone and keep your phone number or choose from a great selection of the latest iPhones and Androids. And, if you’d like to get a 5G phone, H2O Wireless has you covered there, too. The iPhone SE 3rd Gen, iPhone 12 mini, to name just a few, and many new Android devices, like the Samsung Galaxy A32 5G, all support 5G and are available right here.

5G coverage. 5G phones. And a wide variety of plans that include unlimited plans – including unlimited data plans for hotspot – multi-line plans, pay as you go plans, tablet plans, and our brand new 12 month plan (for as little as $8.33 a month!) you can’t go wrong. Plus, there’s no contracts, no hassles, and definitely no locking your phone to our network.

H2O Wireless makes it easy and budget friendly to stay connected to your family, friends, work, your favorite shows, podcasts, news outlets – your whole world – for less. That’s what makes us refreshing. different. wireless. See for yourself and get the most out of your phone today!



Posted 3 weeks ago