If you're using a Pixel 6 or 7, turn off your mobile data until Google deploys the patch (expected 20th March, hopefully sooner given the situation).
Alternatively, what you actually need is to turn off both Wi-Fi calls and voLTE.
On a GrapheneOS phone you can easily disable Wi-Fi Calling from the settings (was disabled by default for me). I didn't find a way to disable voLTE explicitly, but AFAIU turning off the "Automatically select network" settings and choosing your operator's 3g network should to the trick. But you may prefer to play it safe and disable mobile data altogether. That's what I'm doing for now.
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Warren Togami (@wtogami) on X
According to Google Project Zero they discovered 0-day "Internet-to-baseband remote code execution" affecting many millions of Samsung and Pixel 6+...
