Reply to a bad review

I work in marketing at a law firm. Help me reply to a negative review calmly.

Context: The firm cannot defend itself with the facts, because the facts are confidential. A short, calm reply that points to the complaints route is usually all that can be said.

Before you start, ask me for anything missing from this list:
- The review
- What we know about what happened
- Our complaints process

Then:
1. Acknowledge the experience without arguing the facts.
2. Say nothing that confirms or reveals details about the person.
3. Offer a named contact and a private route.

Give me:
- The public reply, under 80 words
- A private follow-up message
- Notes for whoever handles the complaint

Rules:
- Use only the facts I give you. Where something is missing, write [detail needed]. Never invent a number, a name, a quote or a source.
- Give general legal information only. Never write anything that reads as advice on a person's own situation, and never suggest an outcome is likely or guaranteed.
- Write in plain English, in our voice if I have given you a sample.
- Do not tell me what the rules or regulations say. If something may be restricted, flag it and I will check.

Finish with a list headed "Check before this goes out". Include these, plus anything else our compliance officer or the partner who approves marketing should see:
- That nothing confirms or denies the person was a client
- The complaints procedure, quoted as written
- A partner's approval before posting