I could be wrong, but I don't think SIM cards nor phones ever know their mobile number (I've asked a separate question about that). What I'm sure about is they identify themselves to the network using the IMSI of the SIM card (and proves that it indeed is the card associated to that IMSI by crypto based on the card's symmetric KI key) and from there use the random TMSIs assigned to them by the network.

The phone numbers are added by the mobile network infrastructure down the line. You can very well have multiple numbers tied to a single SIM card and phone, and you can theoretically change your number in a matter of seconds (though in reality most mobile network infrastructure is legacy crap that won't allow it, but technically there is nothing preventing this from happening if carriers were using decent software).

*The iPhone is an exception, but I believe its knowledge of its own number comes from the "activation" magic that happens when you first boot an iPhone after reinstalling its OS, where it checks your SIM lock status, submits your ICCID and other unique info to Apple which most likely talks to the carrier's infrastructure and then sends back the returned number as a convenience in addition to the mandatory data returned by the activation process (notification and iMessage/FaceTime related client certificates).

Phones don't even know their phone number. Sure, there is a number field in the SIM card that can be updated remotely by the carrier, but most importantly there is no guarantee that field is even set or is set to the correct number. Phones identify themselves to the network using the IMSI of the SIM card (and proves that it indeed is the card associated to that IMSI by crypto based on the card's symmetric KI key) and from there use the random TMSIs assigned to them by the network.

The numbers are added by the mobile network infrastructure down the line. You can very well have multiple numbers tied to a single SIM card and phone, and you can theoretically change your number in a matter of seconds (though in reality most mobile network infrastructure is legacy crap that won't allow it, but technically there is nothing preventing this from happening if carriers were using decent software).

I'm far from being an expert on the subject, but I don't think SIM cards nor phones ever know their mobile number*. Instead, they identify themselves to the network using the IMSI of the SIM card (and proves that it indeed is the card associated to that IMSI by crypto based on the card's symmetric KI key).

The phone numbers are added by the mobile network infrastructure down the line. You can very well have multiple numbers tied to a single SIM card and phone, and you can theoretically change your number in a matter of seconds (though in reality most mobile network infrastructure is legacy crap that won't allow it, but technically there is nothing preventing this from happening if carriers were using decent software).

*The iPhone is an exception, but I believe its knowledge of its own number comes from the "activation" magic that happens when you first boot an iPhone after reinstalling its OS, where it checks your SIM lock status, submits your ICCID and other unique info to Apple which most likely talks to the carrier's infrastructure and then sends back the returned number as a convenience in addition to the mandatory data returned by the activation process (notification and iMessage/FaceTime related client certificates).

I could be wrong, but I don't think SIM cards nor phones ever know their mobile number (I've asked a separate question about that). What I'm sure about is they identify themselves to the network using the IMSI of the SIM card (and proves that it indeed is the card associated to that IMSI by crypto based on the card's symmetric KI key) and from there use the random TMSIs assigned to them by the network.

The phone numbers are added by the mobile network infrastructure down the line. You can very well have multiple numbers tied to a single SIM card and phone, and you can theoretically change your number in a matter of seconds (though in reality most mobile network infrastructure is legacy crap that won't allow it, but technically there is nothing preventing this from happening if carriers were using decent software).

*The iPhone is an exception, but I believe its knowledge of its own number comes from the "activation" magic that happens when you first boot an iPhone after reinstalling its OS, where it checks your SIM lock status, submits your ICCID and other unique info to Apple which most likely talks to the carrier's infrastructure and then sends back the returned number as a convenience in addition to the mandatory data returned by the activation process (notification and iMessage/FaceTime related client certificates).