I know everybody says how bad SMS 2FA is, and how we should replace it with the next cool thing $BIGCORP invented (thus requiring you to have an account with them, which only defers the problem).

But couldn't we pressure the telecoms to improve it?

I have an idea that would make SIM swaps way harder to execute. Namely a website that wants to authenticate you should be able query the telecom for some kind of SIM card ID. This would happen before sending a 2FA code.

With such a feature it would be easy to store the SIM card ID in a database when enrolling the phone number. Later when the user tries to authenticate and the ID does not match what saved before, the account is locked out. For enterprise accounts you would need to explain yourself to IT and for personal accounts a fallback 2FA would have to be used. Alternatively the authentication would be delayed for a few days to give the legitimate owner of the SIM card time to react.

Another thing that could be added on top of this is to send a SMS to the old "inactive" SIM, alerting the original owner of the attack.

EDIT: To add to this, here are some advantages of SMS 2FA over time based OTP or passkeys:

1. My grandma can use it with her dumb phone and poor digital skills. 2. Your SIM card will most likely survive if your phone is destroyed due to water or physical damage. (Sadly not true for eSIM) 3. You can dictate an SMS/OTP code over the phone, or forward it to somebody you trust. 4. Banks can append a short description of what you are currently authorizing. It can tip you off in case your computer is infected with malware, or you are victim to one of those TeamViewer scams.