The "vast majority" of phones in the UK received a trial emergency alert on Sunday, April 23 at 3pm, as the government tested out a new safety system designed to inform the public about certain dangers.
But some people are claiming that their phones are still buzzing and the siren is sounding with the alert days after it should have originally been received.
Deputy Prime Minister Oliver Dowden hailed the alert as "the sound that could save your life" as it may be used in the future to warn people about things like flooding, fires and extreme weather.
