[shiftpgdn]

Just buy one and remove the SIM card.

[i80and]

They often have eSIMs I think, but (depending probably on the car) pulling the modem's fuse can be safe. That's the case for the VW ID.4 at least.

[wizzwizz4]

I want the car to be able to contact emergency services, but not to otherwise be able to use the cellular network. Is there a good way to sabotage the eSIM, without otherwise breaking the modem? (This would still allow the car to be tracked via IMEI, but I'm not too worried about that: anyone capable of that is also capable of tracking my actual phone, and anyone buying that data will already know what car I own.)

[Nextgrid]

If the modem has no fuse, physically damaging the NIC chip in the module will also work.