Start by gathering your receipt or payment record, photographs, messages and any other evidence of the problem. Contact the trader promptly in writing, explain what went wrong and say what outcome you are seeking; under the Consumer Rights Act 2015, your options may include a repair, replacement, price reduction or refund, depending on the circumstances and timing. If the trader does not resolve matters, check whether it belongs to an approved alternative dispute resolution scheme and contact your card provider about possible protection. Citizens Advice can explain your options, while a solicitor regulated by the SRA may help with complex disputes.