Axios reported this claim and also reported there have been no verified examples of a phone receiving the broadcast as of an hour ago.

https://www.axios.com/newsletters/axios-pm-76a155d0-9b02-11f...

Israel often imposes internet blackouts in Gaza so it could also be likely that word just hasn’t made it out.

https://www.reuters.com/world/middle-east/gaza-hit-by-teleco...