Architecturally there's no binding between phone number and subscriber identity except at the very edge of the network, for the very smallest retail customers.

Architecturally there's no binding between phone number and subscriber identity except at the very edge of the network, for the very smallest retail customers. There is a design to federate this binding throughout the ecosystem using a PKI called STIR/SHAKEN [0], but it's absolutely a hard technical problem to get that rolled out 100% without breaking things. [0] https://transnexus.com/whitepapers/shaken-as/ https://transnexus.com/whitepapers/shaken-as/