The most effective complaints in English are noticeably calm. Politeness is not weakness here — it keeps the other person able to help you.

The structure

  1. State the problem — factually, no adjectives
  2. Say what you expected
  3. Say what you want — this is the part people skip

"I ordered this on the fifth and it was due on the tenth. It's now the eighteenth. I'd like either a delivery date today, or a refund."

Opening phrases

  • "I'm afraid there's a problem with…"
  • "I wanted to raise an issue with…"
  • "This isn't quite what I was expecting."
  • "I've been trying to resolve this since Monday."

Being firm without being rude

  • "I understand it's not your fault, but I do need this resolved."
  • "That's not really acceptable, I'm afraid."
  • "I've been told that twice already."
  • "What can you do for me today?"

Escalating

  • "Could I speak to a manager, please?"
  • "Is there someone else who can authorise this?"
  • "What's the next step if this can't be resolved here?"

Asking for a specific outcome

  • "I'd like a refund."
  • "Could you replace it?"
  • "I'd like this in writing, please."
  • "Can I get a reference number for this complaint?"

The detail that matters most

Get names and reference numbers, every time. "Could I take your name?" at the start of a call changes the tone of everything that follows, and gives you something concrete if you have to call again.

Describe the problem, not your feelings about it. "It arrived broken" works better than "this is unacceptable service".