People are claiming their phones are still going off with the government's emergency alert days after it was supposed to be sent.
The test was supposed to go off on Sunday at 3pm on all devices that were using 4G and 5G networks in the UK.
Government say future alerts could be vital for dangerous emergencies and Deputy Prime Minister Oliver Dowden called the associated buzzing noise the "sound that could save your life".
The sound could be heard in the event of impending dangers like severe flooding, extreme weather, and fires.
The Cabinet Office said the “vast majority of compatible phones” received the alert on time on Sunday.
But even days after the test, people are reporting a confusing delay.
The Government have told the Mirror that they will shortly be releasing an update, which will address the matter and give feedback on the trial.
Many have complained on twitter about being woken up in the early hours of the morning but the sudden noise.
Danny Wisniewski, of Slough, Berkshire, says he was disturbed by the alert at 2.22am.
“It scared the life out of myself and my wife as we were fast asleep and wondered what was going on," he told The Sun. “It was the same alert I had on Sunday.”
Derby Plumber Mark Peters, 54, says it came through at 8am and he told the publication: “It doesn’t bode well if this is supposed to be keeping us safe and alert.”
It has been suggested the delay was caused by mobile phone masts continuing to broadcast the message after the end of the test.
A poll conducted by money saving expert Martin Lewis found that 21 per cent of his followers didn’t get the alert.
Government spokesman said on Sunday night: “We have effectively completed the test of the UK-wide Emergency Alerts system, the biggest public communications exercise of its kind ever done.
“We are working with mobile network operators to review the outcome and any lessons learned.”
Mobile phone giant Three responded to customers who reported that they didn't receive the alert.
“We are aware that a number of customers have not received the test alert," they said.
“We are working closely with the Government to understand why and ensure it doesn’t happen when the system is in use.”
Some may choose to opt-out for a number of reasons - and charities are even warning the alert could be dangerous for domestic abuse survivors.
People who experience abuse may have a second phone they use to call for help and some experts recommended people turn off the alert.
Emma Pickering, senior operations manager for the technology-facilitated abuse and economic empowerment team at charity Refuge said survivors can't use an "everyday phone."
She said: "We know that perpetrators are monitoring devices to make sure that they're not contacting agencies, they're not sharing any information with anybody to say that they're a victim, they're not trying to seek help or plan to leave the relationship."
