An Adelaide mother and her autistic son would have missed out on last night's Elton John concert because of ticket fraud — were it not for the random kindness of a nearby stranger.

Key points: Adelaide woman Samantha Wells paid $388 for two seated tickets to Elton John's concert

Adelaide woman Samantha Wells paid $388 for two seated tickets to Elton John's concert She was told that up to 200 people had also been turned away due to fake tickets

She was told that up to 200 people had also been turned away due to fake tickets South Australia's Consumer Affairs Commissioner is investigating

Samantha Wells purchased presale tickets to the musician's concert from ticket reseller Viagogo earlier this year, but ran into problems when she reached the gate last night.

When Ms Wells and her son got to Adelaide's Botanic Park, they were redirected to the ticket window.

"I went over to the ticket window and she said 'these tickets aren't valid, they're not legit'," she said.

Ms Wells said she paid $388 for two seated tickets, because her son's sensory sensitivities mean he likes to sit.

"I bought the tickets for my autistic son for his recent birthday, and he was very, very excited, as you can imagine," she said.

"I was absolutely devastated for him, as I knew the tickets had sold out … I was thinking 'oh my god, what am I going to do?'"

Ms Wells was told by staff that she could still purchase general admission, so she began to transfer money between accounts to buy the replacement tickets.

"I was all ready to pay, and then this lovely, beautiful gentleman leant over and said 'I'm paying for your tickets to get in'," she said.

"I said 'thank you immensely', but by the time we had actually gathered our tickets, I waved to him and said 'thank you, thank you, thank you' … he'd already gone to go on in.

"I never got to properly thank him, my son didn't get to thank him because I made him stand to one side because he was getting all flustered."

Samantha Wells and her son James were sold fake tickets online. ( Supplied )

Ms Wells said she was far from alone in being deceived, saying "up to 200 people were denied entry last night because of these dodgy tickets".

Elton John is currently in Adelaide as part of his global farewell tour, with the second of two shows scheduled for tonight.

The British pop legend is among many big name acts — including comedian Michael McIntyre, singer-songwriter Shawn Mendes and actor Hugh Jackman — to have been targeted by ticket scalpers in recent months.

Hip hop trio the Hilltop Hoods slammed Viagogo during a recent national tour, after copping harsh feedback from fans over inflated prices beyond their control.

'Don't use Viagogo', Commissioner urges fans

South Australia's Commissioner for Consumer Affairs, Dini Soulio, said he was investigating after being notified of the fake tickets for last night's concert.

Consumer Affairs Commissioner Dini Soulio said people should avoid buying tickets on Viagogo. ( ABC News: Angelique Donnellan )

He said it was concerning that people had bought tickets, made arrangements to attend the event and "have the embarrassment of being refused" at the gate.

"Since this was raised with me, I've been in contact with Viagogo for most of the morning, trying to get to the bottom of what's going on," he said.

"They've given an undertaking to try and address issues around refunds but, as I say, if you're standing at the gate, a refund's not going to help you at the time."

Mr Soulio recommended people avoid Viagogo's site due to the number of complaints about tickets sold on it, reiterating comments he made earlier on commercial radio: "I'm happy to say, don't use Viagogo".

"The number of issues we are seeing with Viagogo in relation to resale is that there is significant risk with people who are selling on that site," he said.

"People are spending hundreds of dollars on tickets to this concert, and similar concerts, and that doesn't take into account the travel and hotels and babysitters and other things, so people are significantly out of pocket because of this."

Problem could be repeated at second gig

Ahead of Elton John's second concert in Adelaide tonight, Mr Soulio urged anyone refused entry to follow up with authorities.

"It is an issue for tonight," he said.

"Ticketmaster are giving people a letter at the box office if they are refused entry, to be evidence of the fact that they were refused, so they can use that as part of their refund process.

"Anyone who attends the concert tonight and is refused entry, we encourage them to head over to the box office and get some proof that they were refused entry, to print off their tickets and then contact my office."

Viagogo is a "secondary marketplace" and does not feature prominent branding. ( ABC News )

Tour promoter Michael Chugg said he was sorry that people who had unknowingly purchased invalid tickets were not allowed entry.

"We can't let people in who have false tickets because if we do that, we're validating these bootleggers," he said.

"Twelve months ago a show like that would have had probably 1,000 false tickets, so we are winning.

"The industry are talking to Google once again about removing them [Viagogo] once again from the page [top search results]."

Ms Wells said she planned to contact consumer affairs authorities to check on her refund options, but has not contacted Viagogo.

"They're in Switzerland, and there's no way I can afford to ring Switzerland," she said.

"Let's just make sure this doesn't happen to other people, because other people paid a lot more than I did. Make sure you go to the [websites] like Ticketmaster … not these other places."

In a statement, Viagogo said it would help affected fans secure refunds.

"Any fan that experiences problems with their tickets in gaining entry to last night’s Elton John event should contact Viagogo as soon as possible so we can help secure your refund," a spokesperson said.

"As with all tickets on our platform, viagogo provides a guarantee that in the rare instance a customer has a problem with a ticket, we will either find a replacement ticket or give a full refund.

"We have become aware of some fraudulent activity that has resulted in tickets purchased with stolen credit cards on other platforms and re-sold on our platform. We are doing everything we can do resolve this issue."

But the spokesperson denied selling "fake" tickets, saying Viagogo remained a "safe and transparent service".

Earlier this year, the Federal Court found the ticket reseller engaged in misleading and deceptive conduct through Google advertisements and claims about the scarcity of tickets.