That wouldn't be a problem in phones where the radio part is screened from the system (Pinephone?) so that implementing encryption can be effective. The SIM might be tied with my me, but any eavesdropper would see only noise because the outgoing data is encrypted by the system before entering the radio hardware and is decrypted by the system after leaving it. They can know I generated some traffic at a certain moment, which is the same information they could get from the carrier operator, but that's about it.