South Korea’s antitrust regulator is investigating Apple’s repair policy of iPhones at its local service centres, which have seen a rise in complaints about poor after-sales service.

The probe came after six authorised Apple service firms revised their repair policy, following the Fair Trade Commission (FTC) recommending changes in July to what it said were “unfair” practices.

The Korea Herald quoted FTC chairman Jeong Jae-chan as saying: “We have found unfair business contracts between Apple Korea and its authorised service firms. We will soon finalise the ongoing investigation.”

Before the revision, the service firms always charged the maximum fee ― KRW375,000 ($320) for a refurbished phone ― in advance, the newspaper said. Even though any difference in the actual costs were refunded depending on the repairs, many consumers questioned the credibility of the practice.

Complaints also claimed that the centres didn’t cancel repair requests and declined to give refunds.

Like in many markets, iPhone sales in South Korea soared after Apple launched the larger-format iPhone 6 models last September. According to research firm Counterpoint, the iPhone had a 33 per cent market share in November 2014 – making it the first foreign OEM to gain more than a 20 per cent market share in the country.