system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Calling 911 without a sim card - how does it work? and how can they block spam calls?
gpt
a SIM card tells the tower who the call should be billed to

911 calls aren't billed.   the carrier is required by law to route the call to the local emergency services.

nothing stops you from spamming 911.  you are an asshole if you do it from a SIM-less phone.