Respond to a difficult client without losing your cool or over-conceding

Act as a customer service consultant who's an expert at defusing tense situations: someone
who knows how to calm an upset person without sounding defensive, without over-conceding, and
without risking the business relationship. I'm going to give you the client's message and my
side of the story. Your job is to write my response.

Situation details:
- Client's exact message or complaint: [PASTE THE CLIENT'S MESSAGE HERE]
- What actually happened from my side: [YOUR VERSION OF THE FACTS]
- Whether there was a mistake on my end: [YES, THIS HAPPENED / NO, BUT I UNDERSTAND WHY THEY'RE UPSET]
- What I'm willing to offer as a solution: [E.G. PARTIAL REFUND, REDO THE WORK, DISCOUNT, JUST AN EXPLANATION]
- What I'm NOT willing to give: [E.G. FULL REFUND, IMPOSSIBLE DEADLINE, FREE EXTRA WORK]
- Channel where I'll respond: [EMAIL / WHATSAPP / PUBLIC REVIEW / SUPPORT CHAT]
- How I want to sound: [WARM BUT FIRM / VERY FORMAL / CASUAL, based on my brand]

Write the response following this structure, without labeling each part, as one natural,
flowing message:
1. Acknowledge what the client is feeling (without admitting fault I don't actually have).
2. Clarify the facts calmly, in one or two sentences, without sounding like an excuse or a
   legal statement.
3. Offer the concrete solution I'm actually willing to give.
4. Close by leaving the door open to keep working together, without sounding desperate.

After the response, add a short "Why this works" section explaining in 2-3 lines what
conflict-resolution technique I used and why it keeps the situation from escalating.

Rules:
- Never apologize for something that, based on my details, wasn't actually my mistake.
- Never promise anything I didn't mention in "what I'm willing to offer."
- Don't invent names, amounts, or dates I didn't give you: if something is missing, write
  [detail to verify] instead.
- Maximum 150 words in the response, ready to copy and send as-is.