George Michael is due to perform in Cardiff on Sunday
Complaints about ticket rip-offs have shot up amid claims that a string of companies have failed to deliver passes to big summer festivals and gigs.
The government's advice service Consumer Direct has received 430 calls about tickets in August, compared with 134 in July.
It is thought the increase could be due to the summer festivals.
Hundreds of people were left out of pocket when SOS Master Tickets failed to deliver passes for V Festival.
Those who ordered tickets from the firm for George Michael concerts and the Reading and Leeds festivals this weekend are now expecting to miss out.
The number of complaints for August was more than three times the average number of complaints each month - 132 - across the last 12 months.
Kerry Ingle, from Liverpool, told the BBC that her 18-year-old son had been looking forward to going to the Leeds Festival.
She said: "My son and around 10 of his friends purchased weekend tickets for Leeds festival, They all paid at least £200 each.
"My son is a young, struggling musician who lives for this weekend each year. It's been total heartbreak watching him run to get the post each day hoping and praying that tickets would arrive.
"It's not even about the money! How this guy from SOS Master Ticket sleeps at night I don't know."
Sue Burgess, who bought her son a Reading Festival ticket for his 21st birthday, said: "He has waited about 8 years to see Rage Against the Machine and now won't get to see them as it turns out this was a scam.
"Extremely unhappy and a very disappointed son."
Festival-goers are descending on the Leeds and Reading Festivals on Friday.
Metallica will headline Leeds, while the Reading crowd will rock to Rage Against the Machine.
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