Thousands of customers aggrieved at the big bills they received after signing up for the Crazy Frog ringtone could receive refunds.
Over 300 people complained about the service
Watchdog Icstis has ordered MBlox, the service provider behind the ringtone, to refund the 338 people who complained directly to it.
But it is confident that others affected by the service will also get a goodwill refund as long as they can provide the appropriate evidence.
MBlox has also been fined £40,000.
It argued that it should not be held responsible for the actions of a third party.
MBlox is the service provider behind the ringtone and therefore the one with its name on the contract with the telephone provider.
But the Crazy Frog character was actually the brainchild of ringtone-maker Jamba.
It was a huge hit during the summer and was the first ringtone to make it to the top of the UK singles charts.
It netted an estimated £10m for Jamba and MBlox but thousands of customers found themselves with inflated bills.
Many were unaware that by texting a number to receive the ringtone, they were also signing up for a series of at premium rate reverse-charge texts from Jamba.
The ruling from premium rate services regulator, Icstis, found that while a great deal of thought had been put into producing the Crazy Frog advertisements, the same could not be said about the terms and conditions.
These terms omitted significant information and were unclear about what the service entailed, it said.
It fined MBlox £40,000 and ordered it to refund those customers who complained directly to the watchdog.
"The Hearing Panel has made clear that consumers should not be made to work to find out what any premium rate services involves or costs," said Icstis director George Kidd.
"Although they found there was no fraudulent or malicious intent behind the service, the companies concerned showed a careless disregard and unprofessional attitude to consumers in failing to be clear on the exact nature of the service," he said.
MBlox, which was fined £2,000 in April for a promotion that involved unsolicited text messages, has argued that Icstis should in future go after the content providers directly.
"In future the regulatory framework should make the people who create and promote mobile content accountable for the content transmitted to consumers and the marketing practices they adopt," said the company in a statement.
Under current legislation, Icstis is only able to regulate service providers.