My phone won’t allow me to send out messages to just a few other numbers, my phone carrier (O2) cannot seem to work out why. Would it help rectify this issue if I turned Wi-Fi calling on ? Not sure if that’s the way to go , any ideas ?

genna97 wrote:

I have a US phone that I’ve put an UK E Sim onto, turned off my US line whilst here in the UK. This shouldn’t cause an issue with my messages should it?

iMessage or SMS?

iMessage (Blue) -

• iPhone to iPhone: requires internet (Either over WiFi or Cellular Service) as it is sent over internet protocol. Needs Activation on your device.
• iPhone to Android: Not available

SMS/MMS (Green) -

• iPhone to Android: does not require any internet it is sent over cellular voice protocol. Needs to be enabled by your Carrier for the SIM used by you.
• iPhone to iPhone: When iMessage is not activated or the device is not connected to the internet either over cellular or WiFi
• You need to have an SMS/MMS plan enabled by your carrier for the SIM/eSIM that you use on your device. Apple Inc does not provide SMS/MMS services.

It will turn from Blue to Green if you have enabled "Send as SMS" and whenever your iPhone is not connected to the internet it is sent as SMS (green) to all iPhone users.

With WiFi calling you can only make calls and not send messages.