The sim basically doesn’t matter. The imei identifies the phone to the network, the sim identifies the subscriber. So the network sees phone x unknown subscriber prepaid carrier. Airplane mode does not prevent the phone system from triangulating your phone, or from turning the baseband on remotely even when the phone is “off”.

The carrier definitely knows where you live if you take your phone to your house at night, even if it is off. The only way to prevent that is to put it in a faraday pouch at your “airplane mode” checkpoint.

Why do you think basically zero phones have trivially removable/changeable batteries? Any phone that clams to be security first and doesn’t at least have a switch (an actual switch) that disconnects the battery altogether is a joke.