Write a Complaint That Actually Gets a Result

I need to write a complaint to a company or service provider, and I want it to actually get a result — not just disappear into a black hole.

Here are the details:

Who I'm complaining to: [company or organisation name — e.g. my energy provider, a retailer, a restaurant, my broadband company]

What happened: [describe the problem — e.g. product arrived broken, engineer didn't turn up, I was overcharged, rude staff, service wasn't as described]

When it happened: [date or rough timeframe — e.g. last Tuesday, over the past three months, on 5th March]

What I've already done about it: [e.g. called customer services twice, spoke to a manager, sent a message on their website, nothing yet]

What I want them to do: [e.g. give me a full refund, replace the item, fix the issue, apologise and compensate me]

Any reference numbers or details: [e.g. order number, account number, booking reference — or leave blank if you don't have one]

Please write me a complaint email that:
- Opens with a clear, calm statement of the problem
- Includes the key facts and dates without waffle
- Mentions what I've already tried to do to resolve it
- States clearly what I want them to do and by when
- References my consumer rights where relevant (e.g. Consumer Rights Act 2015, right to a refund or repair)
- Is firm and assertive but stays polite and professional throughout
- Ends by saying I'll escalate to the ombudsman or trading standards if I don't hear back within a reasonable timeframe
- Uses British English throughout

Keep it to one page — concise and to the point. The tone should be confident and no-nonsense, like someone who knows their rights but isn't looking for a fight.