My ex son-in-law bought my granddaughter a mobile ‘phone, which failed during the warranty period. However the manufacturer won’t honour the warranty because it had been fitted with a counterfeit case by the retailer. Now the retailer won’t refund the money because I wasn’t the purchaser of the ‘phone.
As a general rule manufacturers will honour warranties whether or not the claim is made by the purchaser. Obviously yours is a special case, since there appears to have been a breach of the terms of the warranty. The Contracts (Rights of Third Parties) Act 1999 can help in these circumstances, but your ex son-in-law would have had to tell the shop where he bought the ‘phone your granddaughter’s name in order for her to become a party to the contract. She should ask her father to take the ‘phone back.