Two Numbers, One Phone

Did you know that most smartphones manufactured in the last few years support more than one simultaneous number? Apple introduced support for Dual SIM in their products several years ago with the iPhone XS and XR, but in my experience it is a largely unknown feature. What is an eSIM, why is is valuable, and how am I taking advantage of it now?

In order for cell phones to work, they needed a tiny SIM¹ card. The SIM card stored credentials and identification data needed for the cell phone to connect to a provider’s network, and without one a cell phone could not make calls, send texts, or use cellular data to browse the internet. In some cases, a SIM could be moved from one phone to another to transfer service as long as the new phone used the same radios to connect to cell towers². SIM cards could also be replaced to change providers or when traveling abroad (since most US providers did not offer native international service).

The ability to have two SIM cards in a phone was introduced in 2000 but didn’t pick up major manufacturer support until around 2010 (and even then it was limited to a few models)³. It wasn’t until the introduction of eSIM (or embedded SIM) technology that support for multiple SIMs became widespread.

Manufacturers started adding eSIM capabilities as far back as 2017, when Google’s Pixel 2 was released, but it wasn’t until the more popular iPhone XR and XS were released in 2018 that eSIM conversations moved into the mainstream. eSIM offered several advantages:

• Easier to switch networks since the need to order and swap a new physical SIM card was eliminated.
• Supports up to five virtual SIM cards, which made it easy to switch between networks depending on your location (e.g. traveling).
• SIM cards could go bad or be lost, but eSIM cannot since it is embedded in the device.
• Uses less physical space, which opened the door for devices like cellular connected smart watches.

Use of cell phones has become a necessity in most workplaces, but not all employers 1) provide phones for their employees or 2) provide a stipend to help pay for the use of a personal device. Because an eSIM is considered a separate line and is charged as such, I never explored the use of one for a work number since it would have meant additional out of pocket costs to me. Instead, to keep my personal number personal, I hobbled along with tools like Google Voice.⁴

I started a new job this fall and they generously provided a cell phone stipend. I learned that most employees used their cell phones exclusively and that few had desk phones, which made sense given the mobile nature of their roles. I really liked that approach as long as I could separate out work and personal calls, and that’s when I decided to investigate eSIM again.

Unsurprisingly, activating and using an eSIM was easy—just tell your provider you want to add a line and give them a unique identifier from your phone. I was able to designate each line with a label and can even define which line to use for calls and texts based on contact. When making calls, there is a toggle above the dialer that lets me pick which line to use, and incoming and outgoing calls and texts show the first letter of my line designation (“P” for Personal and “B” for Business) so I know at a glance which one was used. It’s very slick and perhaps even a little fun, and I no longer feel I need to be guarded about who has my “cell” number.