Keep repeating what is wrong with the goods or service and what you want done about it. Sometimes it's important to write to a trader. Keep a copy of your letter. Send copies of documents. Do not send originals as they may get lost.
Many traders belong to specific organisations for their industry.
Some have complaints handling schemes that can be used to resolve a complaint. If your complaint is about the way a trader treated you or your complaint this is the best avenue for you. There is often either no charge or a small fee to use these services. The tribunal can hear claims to do with a breach of contract, Consumer Guarantees Act, Fair Trading Act.