eSIM vs dual SIM — how they actually work together

These terms get confused a lot — here's the clear version

"Dual SIM" and "eSIM" are related but different things, and understanding the distinction makes travel planning much easier.

What is dual SIM?

Dual SIM means your phone can have two active mobile connections at once. Traditionally this meant two physical SIM card slots. Modern phones often combine one physical SIM slot with one eSIM slot — giving you dual SIM capability without needing two physical cards.

What is an eSIM?

An eSIM is a digital SIM built into your phone's hardware. Instead of a physical card, you scan a QR code and the SIM profile installs digitally. Your phone can then use it exactly like a physical SIM.

How they work together for travel

This is the useful part: most modern iPhones and Android flagships let you keep your regular Australian SIM (physical or eSIM) active for calls and texts, while running a second, travel-specific eSIM for data. Both work simultaneously.

That means:

Checking if your phone supports this

On iPhone: Settings → Cellular — if you see "Add eSIM" and can toggle between two active lines, you're set. Most iPhones from XS (2018) onwards support eSIM; iPhone 14 onwards sold in Australia are eSIM-only (no physical tray at all).

On Android: Settings → Network & Internet → SIMs — most flagship Android phones from 2020 onwards support eSIM alongside a physical SIM slot.

The bottom line

You don't have to choose between your home number and travel data — modern phones are built to run both at once, and that's exactly how a Proost eSIM is designed to be used.