Hi jmarine_,
Thanks for the follow up details! We're happy to provide more information on how cellular networks and phones work.
For your question "If that’s the case with phone calls/FaceTime “it never reached the phone cause it’s off” then how can we still receive text messages and voicemails while it’s off ???", this would be because voicemail/text messages work a completely different way than phone calls.
A phone call is a real time event, meaning you dial a number and press call, the phone connects and sends that call to the other person, they receive the call on their phone and then press answer. For a phone call to work, it requires two phones that are on and connected to the network, and a person actively talking on each end. This is why if you call a phone that is powered off or has no service, it doesn't ring and gets routed right to voicemail.
Now for messages and voicemail, they work in a completely different way since they don't need to occur in real time. So for example, if you call someone and their phone is off or doesn't have service, you'll be sent directly to the voicemail system which is stored on their carriers network. If you leave a voicemail, that message is stored on the carriers voicemail server, and the next time the phone connects to the network, the voicemail server will deliver a notification to the phone letting them know they have a new voicemail.
Messaging works in a similar way. While messages are not permanently stored on the server like voicemail, they will be stored there temporarily until they can be delivered. So for example, if you send a message to someone and their phone is off, when their carrier attempts to deliver it, the network will see that the phone is not currently connected and it will hold those messages in queue on their SMS server until the next time the phone connects to the network. When the phone connects to the network again, the message queue will be released from the server and delivered to the device.
Missed FaceTime calls can show in certain situations if you're using multiple devices. So say for example you have an iPhone and an iPad. You turn off the iPhone, but leave the iPad powered on. Someone then tries to make a FaceTime call to you. Since a device that is associated with your FaceTime phone number has an active connection (the iPad) the call can still come through on that iPad. Now if you don't touch the missed notification on the iPad and turn your iPhone back on, you'll see that missed notification in FaceTime on the phone as well.
Hope this helps. Cheers!
