Spark will simulcast today's Rugby World Cup games free to air on TVNZ after glitches with its streaming service during last night's key All Blacks game.
And customers unhappy with yesterday's service can request refunds, Spark announced this afternoon.
However, unhappy customers would be required to fill in the refund form by no later than 11.59pm on September 29, it has been revealed.
"We will process your refund within 10 working days to the credit card associated with your Spark Sport account," Spark Sport said online.
Spark's video streaming service cut out for some fans during last night's epic All Blacks-Springboks match, with images of the game flickering, pixelating, blurring and buffering, or losing signal altogether.
The provider was forced to air the remainder of the game free-to-air on TVNZ's channel DUKE. But many viewers complained they had not been made aware of the move until late in the game, with some demanding refunds.
Spark this morning apologised for its failings and said it would screen today's games free to air if it was not highly confident there would not be further glitches.
The company said this afternoon it was changing the way the video stream came into New Zealand and believed that would fix the problem.
The change would be made before today's matches, starting with Italy v Namibia at 4.45pm. Ireland play Scotland at 7.15pm and England play Tonga at 9.45pm.
However, it would still simulcast all today's coverage free on TVNZ Duke to give customers "full confidence" that they would be able to watch the matches.
"We are confident Spark Sport will provide a good experience tonight, but if customers for any reason are unhappy with their stream, they will have the opportunity to watch on TVNZ DUKE."
Various refund options were available for customers unhappy about last night's viewing.
"Customers who feel unhappy with their viewing experience of the All Blacks v South Africa pool match pass can receive a refund: customers who purchased an All Blacks vs South Africa Match Pass can receive a full refund; those who purchased a Tournament Pass and wish to leave the service can also receive a full refund; and those who wish to carry on with the service, can receive a partial 15 per cent refund of their Tournament Pass price.
"Unhappy customers who have activated a Spark Sport subscription via a voucher code can also receive a full or partial refund."
TVNZ DUKE is available on channel 13 or DUKE on Sky channel 23. Tonight's matches will not be available through the TVNZ website or TVNZ OnDemand app.
Broadcasting minister Kris Faafoi told the Herald Kiwis expected better than the service they were provided last night.
"We will leave it to Spark to answer the concerns around last night, but we are happy there was the contingency with TVNZ's Duke channel and that it kicked in for viewers when Spark Sport identified issues," he said in a statement.
"We will let Spark go through their technical process before we make any further comment but it is obvious that with an event like this Kiwis expect better delivery than last night."
Faafoi was being kept briefed on the issue.
Rugby fans have ripped into Spark on social media. One woman said last night's game was "like watching 80s TV, the quality was so bad", while another said it was like the game had been played on the moon.
The streaming issues were "a failure on our part and we apologise to customers for that", Spark Sport spokesman Andrew Pirie told Radio Sport's Jim Kayes this morning.
Spark had been monitoring the quality of the video stream and could see it was starting to fluctuate midway through the first half of the game, Pirie said.
"That wasn't acceptable and so we made an immediate call as quickly as possible and basically decided to start simulcasting the game on TVNZ Duke."
He said the vast majority of customers had continued watching on Spark Sport. "But clearly it wasn't good enough and we apologise for that."
He also acknowledged a banner on the Spark Sport site advising customers of the switch to Duke had not gone up fast enough. Many customers have complained they didn't know it was being screened live on Duke after the Spark issues.
Pirie said technical teams had been working overnight to identify what went wrong. "We believe the issue does lie within the international distribution network. And that's how the video stream passes from our streaming platform... based in the United States through to our New Zealand providers."
While the problem was happening offshore, it was Spark's problem and the company was "owning" the issue.
Asked how embarrassing this was for Spark, he said: "This is not a great experience for us but more importantly it's not a great experience for our customers. These sorts of things are never a good look."
It was too hard to say how many customers were affected, but he believed it was "a small percentage" at any one time.
Spark Sport operations has screens on the wall showing every device that the game is being streamed to. It was clear that different devices were having problems at different times.
Other customers were experiencing "localised issues" due to their own devices, and Spark had been helping them through that, Pirie said. He said the streaming issue had not been happening in the earlier games.
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Spark CEO Jolie Hodson said this morning the company was very disappointed that some New Zealanders did not get "the experience they deserved" during an important match.
"Making a quick decision to give them an alternative means to watch the All Blacks was the right thing to do. We apologise to all impacted customers and we will be working with our partners to rectify what happened and ensure the rest of the tournament goes well."
Spark customers - many of whom had paid between $60-$90 for the privilege of streaming games live through Spark Sport for the six-week tournament - took to social media to complain, with some asking for their money back.
One customer said they had predicted the "absolute shambles" and called for an apology and full refund - as well as making remaining games free to air.
Another said they had watched the game in "glitchy, blurry quality" only to find out it was free on Duke in the last three minutes.
A Dunedin man asked for a refund but Spark only offered him $9 of the original $90 he paid for a Tournament Pass.
Denzell Wiese Christian sent the Herald screenshots from his chat with a helpdesk assistant at Spark Sport.
He had asked for a refund on his Tournament Pass but was only offered 10 per cent back.
He was initially offered help to troubleshoot his device before he made it clear he had found another way to watch the game. The assistant then ended the conversation, the chat desk screenshots show.
However, another Facebook commenter said she had been offered a complete refund of the $90.
The glitches appeared to hit customers randomly, with some in Auckland with new TVs and fibre getting appalling visuals while other rural customers said their streaming worked fine.
Spark said most of its customers had continued to stream the game, with streaming peaking at 132,000 devices and dropping to 126,000 by the end of the match.
Spark's contingency plan to move games to TVNZ was reported back in February. At the time the Weekend Herald reported Spark had pledged to air games live on TVNZ within five minutes of an outage.
In June last year Spark's managing director Simon Moutter assured Radio Sport listeners the company had "plenty of practice with streaming" and were "technology experts on this stuff".
Earlier this month a survey by Broadband Compare asked Kiwis how they felt about the streaming service taking the Rugby World Cup rights.
Just 11 per cent of those planning to watch the RWC said they were extremely confident the streaming would go well.
Half of Sky customers were not confident, while Spark Sport customers were on the fence.
The company said this morning the root cause of the problem was still being investigated with Spark's international streaming partners, but it was not related to New Zealand's broadband capacity.
In a further statement at 10am, Spark said it had been working with its partners overnight.
"Our technical team believes the issue is within the international distribution network via which the video stream is passed from our streaming platform located in the USA, through to New Zealand broadband providers. The team are working to confirm this and put a fix in place.
"At this time, it is too early to say whether the issue will be fully resolved in time for today's matches. Unless we confident of this, then we will look to simulcast tonight's matches on TVNZ DUKE to ensure New Zealanders have a good viewing experience.
"We intend to make a decision on whether or not to simulcast by 1pm today, to ensure our customers have adequate time to prepare for today's matches."