Dual SIM allows users to use two phone numbers at the same time. For example, you can use
one number for business and another number for personal. Or you can add a local data plan
when you travel outside of the country or region.
Dual SIM card phones also allow you to have separate contact lists within your phone. A dual SIM card phone may use more battery power than a single SIM card phone.
How does a dual SIM card phone work?
With dual SIM card phones, you'll have a primary SIM card slot and a secondary SIM card slot. Typically, the phone's primary SIM card slot is the only one that can be used with your phone plan's data services -- meaning, the megabytes or gigabytes provided by your plan for accessing the internet.
The secondary SIM card slot cannot access data, only calls, and texts.
Can one or both of my SIM cards be eSIMs?
Thanks to the power of eSIM, you no longer need a physical SIM card to manage your calling plan. However, there are some restrictions when it comes to using an eSIM with a Dual SIM card phone.
If you're using a dual SIM card phone, you can use eSIM as your only cellular plan or you may use a physical SIM card for your first cellular plan and eSIM as the second. You cannot use two eSIM cellular plans in your dual SIM phone (unless you have an Apple iPhone 13, iPhone 13 Mini, iPhone 13 Pro, or iPhone 13 Pro Max).
Select Apple iPhones, allow you to use more than one eSIM and, in fact, more than two eSIMs. Depending on your device model (newer Apple iPhones are the only devices with this functionality at this time) you may use up to 20 eSIMs on the same device!
While your phone can contain multiple eSIMs (and therefore multiple phone numbers) only one can be used at a time. To switch from one line to another, you must go into your phone's Settings and enable the line you want to use.
You can learn more about Dual SIM with an eSIM here: https://support.apple.com/en-us/HT209044.