Exactly this. Here in Israel, SMS is used extensively as part of a multi-factor authentication system. I also require my National ID.
To move my phone number (consent or not) between any phone companies requires an SMS, my National ID, and verification of my ID, and personal details in the government database.
To move my phone number (consent or not) between any phone companies requires an SMS, my National ID, and verification of my ID, and personal details in the government database.
SMS by itself is not secure.