To complain about a violation of your consumer rights, start by contacting the company's customer service. Clearly explain your issue and provide any relevant details, such as receipts or order numbers. If the company doesn't resolve your complaint satisfactorily, you can escalate it by writing a formal complaint letter. Make sure to keep copies of all correspondence. For further assistance, you can also refer to the Citizens Advice website or the official gov.uk page on consumer rights for guidance on how to proceed.