Are iPhone users unable to send you text messages after you've switched from an iPhone to a Firefox OS device? This is because text messages between iPhone users are not sent as regular text messages; instead, they are converted by Apple's servers into iMessages format before they are routed to your device.
The solution is easy - just switch off iMessages on your iPhone before you move your SIM card to your Firefox OS phone. Here's how to do it:
Launch Settings on your iPhone.
Scroll down and tap on Messages.
At the top of the screen, turn iMessages to Off.
That's it! Remove your SIM card from your iPhone, put it in your Firefox OS phone and enjoy.
After you've turned off iMessages, incoming messages from other iPhone users should arrive as regular text messages. This could take up to three days, depending on Apple's servers.