Some users of older iPhones may need to wait until March for Apple to keep its promise to replace the phones’ batteries at a reduced cost.

UK and US customers have been reporting on social media that Apple Store staff have informed them of the delay. Apple recently confirmed that it has been slowing down the performance of older iPhones to extend battery life.

The company offered to replace batteries in the iPhone 6 and later models at a reduced price of £25, even if the phone passed Apple’s performance test of keeping more than 80% of its original capacity. Earlier iPhone models, including the 5, 5c and 5s, are not eligible for the battery replacement offer.

Apple originally scheduled the reduced battery price to come into effect at the end of January, but the company has now confirmed that the offer is presently available.

According to a report in MacRumors, replacement batteries for the iPhone 6 Plus are in especially short supply, with added stock not expected until March. A replacement stock of batteries for the iPhone 6 and the iPhone 6s Plus should arrive in about two weeks.

Documentation reviewed by MacRumors said that replacement batteries for the iPhone 6s, the iPhone 7, the iPhone 7 Plus and the iPhone SE should arrive “without extended delays,” but Apple gave no specific time frame.

Apple’s offer to reduce the price of replacement batteries on affected iPhone models came after customers in the US, France and Israel filed lawsuits against the company.