Subscriber identity module (SIM) cards are the key to linking your cell phone with a cellular network. They’re tiny chips inserted into cell phones to connect them with the carrier network and a specific user account (phone number). Most of the time, if you purchase a new phone, you can transfer the SIM card from your old phone into the new one and keep your phone number.

While SIM cards are a great way to transfer data from old phones to new ones, is it possible to buy a new SIM card for an existing cell phone? It depends on the type of phone.

GSM vs. CDMA Phones

There are two types of technology that are used by most modern cell phones: Global System for Mobile Communication (GSM) and Code Division Multiple Access (CDMA). Whichever technology your existing phone uses will determine whether it can swap SIM cards or not.

GSM Phones

GSM phones are the most common around the world. They rely on SIM cards to link the device to the cellular network and the user’s account.

If your existing phone uses GSM technology, there’s a good chance you can purchase a new SIM card for it. You just need to make sure it’s “unlocked” first. Some carriers include software that links the SIM card to the phone’s serial number. If the two don’t match, the phone won’t work. When you unlock a phone, it removes that link and lets you use different SIM cards.

CDMA Phones

These phones don’t use SIM cards at all. Instead, they’re linked to the carrier network and user account with built-in software that can’t be altered. In other words, they’re locked and can’t change carriers.

If you own a CDMA phone, you can’t purchase a new SIM card. The only way to change carriers is to get the device authenticated directly by the service provider.

How to Know Which Type of Phone You Have

Take the SIM card out of a friend’s phone and put it in yours. If your phone doesn’t have a SIM slot, you have a CDMA device and can’t purchase a new card. If it does have a slot, swap the SIMs and call your friend’s phone number. If your phone rings (with their SIM card), you have an unlocked GSM device and can purchase a new SIM card. If your phone doesn’t ring, your phone needs to be unlocked before purchasing a new card.

Send a Mobile Recharge to Any Phone from eTopUpOnline

Whether your device is CDMA or GSM, you can purchase an international mobile recharge online from the best online mobile recharge website: eTopUpOnline. Before sending a mobile recharge, make sure you choose the right carrier for the device. For example, a Digicel recharge only works on Digicel-enabled devices, and a Natcom top up online only works for Natcom-enabled devices. If you want to swap carriers, make sure your phone is unlocked and uses GSM tech, then purchase a new SIM card from the carrier of your choice.