If your iPhone is unlocked, then you can use two different carriers on the same handset. Apple also states that if a “CDMA carrier provides your first SIM, your second SIM won’t support CDMA”.

iPhone SE is a single SIM phone, but if you don't want to go through the hassle, you can also buy an unlocked SIM-free version too.

Seeing “No SIM” or “Invalid SIM” on iPhone? Check your SIM card, restart, or update your carrier settings. Simple fixes often ...

A dual-SIM setup lets you use one phone to make and receive calls and texts from two numbers. It's also super convenient and can save you serious cash when traveling. We show you how to use two ...

On rebooting, the iPhone picked up on the dual-SIM module, reconfigured the Settings app to deal with two physical cards, and Apple’s smartphone ran happily with two physical SIM cards.

If you want to upgrade your iPad to have 3G/4G capabilities, you need to equip it with a SIM card. Our beginners' tutorial explains where to get the right SIM card, and how to do install it.