When Claire Turnham tried to buy Ed Sheeran tickets for her son's 16th birthday, she thought it was going to be an "amazing" family trip.
Instead, she says she was overcharged by £1,150, and the episode has led her to take up a campaign against Viagogo, the secondary ticket website she used.
She set up the Victims of Viagogo group on Facebook to seek refunds for others who feel they have been "ripped off".
"It's affecting people worldwide and it's growing all the time," she said.
Ms Turnham gave her experiences to a House of Commons select committee hearing about ticket abuse on Tuesday.
She said she's been contacted by 425 people from 26 countries in the past six weeks who were charged more than they expected and have had "very frustrating" experiences trying to get refunds.
Birthday surprise backfired
Ms Turnham tried to buy four tickets to see Ed Sheeran in Dublin on 12 April - her son's 16th birthday.
"I have four children - three of them are massive Ed Sheeran fans," she said. "As their mother I thought it would be an amazing experience for us to be able to go to Ed Sheeran together.
"So I thought, as a surprise for them, that I would try and get tickets. The last time I bought tickets was 10 years ago to Rod Stewart. I'm not familiar with the secondary market - or I wasn't until six weeks ago."
She looked for tickets on 31 January, when pre-sale tickets for the gig were made available, but had no joy going through Sheeran's official site and Ticketmaster.
"I went back onto Google and I found Viagogo at the top of the listings, which said, 'We have tickets today, official site', and I just went with that."
Viagogo offers tickets for resale, often at inflated prices. The company declined to send a representative to the select committee hearing and hasn't responded to requests for comment from BBC News.
'I didn't have the money'
Ms Turnham continued: "I knew from the research I'd done that the face value of the ticket was likely to be between £50-£75, so when I saw four tickets for £263 I did a quick mental calculation and thought that sounded about right and I pushed 'buy'.
"I didn't know through any of that process that that price was actually going to be per ticket, and that there were going to be fees on top of that. So actually what it ended up costing was £1,421.
"The day after this, my rent was due and I knew I didn't have £1,421 in my account."
The first transaction failed - but Ms Turnham says Viagogo then processed the transaction a different way and she was charged the full amount.
She received a refund after much persistence and taking her story to the media. "When I was offered my refund I was very glad of it," she said.
"But I started to become aware that other people had become affected and weren't receiving refunds so I started trying to help them... People are contacting me all the time and they're very, very distressed."
She has posted photos on social media of people who have had similar experiences of being charged more than they expected when buying tickets to see stars like Craig David, Bruno Mars, Lady Gaga and Adele.
'You have to be strong'
Many people don't have the energy to keep chasing refunds, she said.
"You have to be able to be incredibly strong to be able to do this because like any other form of abuse it relies on people being silenced and it relies on people being isolated."
Viagogo had a seat at the select committee hearing - but it remained empty.
Nigel Huddleston MP said Viagogo had written to the committee explaining their absence by saying "we do not sell tickets", but instead is a platform for handling tickets.
But the company was roundly criticised by MPs and other expert witnesses for its practises, with Nigel Adams MP saying it made "Stan Flashman look like Mother Theresa".
Ed Sheeran's manager Stuart Camp and gig promoter Stuart Galbraith did give evidence and talked about a Sheeran show at the O2 arena in London in June.
Emotional and physical stress
They said they had written to the four main secondary ticket websites - Viagogo, Seatwave, GetMeIn and StubHub - in advance, asking them not to list any tickets for the show because they would cancel any that were found to have been resold, and fans would not be let in.
"All four sites ignored our requests and all four sites listed tickets at inflated prices, knowing that it's our intention to cancel those tickets and not admit their customers."
Ms Turnham said the threat of not getting in added extra stress to fans who already paid over the odds.
"It's causing not only financial effects but serious emotional and physical effects too," she said.
"As well as all the money issues and how they're actually going to pay for that, it's whether or not their ticket is actually going to be valid. As we've heard today, these people who've paid for Ed Sheeran tickets, at these excessive prices, actually may not be able to get in."
Mr Galbraith offered advice for fans looking for tickets: "Go to the source. If you're buying an Ed Sheeran ticket, go to edsheeran.com because from there you will only be directed to official outlets. The worst thing you could do would be to Google search."
He also pointed fans toward a new guide to ticket-buying published by the Fair Fan Alliance.