Reply to a customer who disputes your invoice

A customer has disputed our invoice. First check each point they raise against the contract and our records, then draft a reply to {{customer_contact}}, so that we agree quickly on what is right, correct what is wrong, and get the undisputed amount paid while anything else is settled.

Their message:
"""
{{customer_message}}
"""

The invoice (lines, amounts, dates, payment terms):
"""
{{invoice}}
"""

What the contract, quote or purchase order says about price, scope and billing:
"""
{{contract_terms}}
"""

Our records of what was delivered or done (delivery notes, timesheets, change requests, emails approving extra work):
"""
{{records}}
"""

What we have decided to correct or offer, if anything: {{approved_changes}}

Part 1, for me: a table with the columns Disputed item, Customer says, Contract says (quoted, with clause), Our records show, Finding (customer is right, we are right, partly, cannot tell). Then the undisputed amount, with the arithmetic.

Part 2, the reply, under 220 words:
1. Thank them for raising it and say we checked each point.
2. Where they are right, say so plainly and say what we will do: a credit note or corrected invoice, only as approved above.
3. Where the invoice is right, explain why in one or two sentences each, pointing to the clause or record, attached or quoted.
4. Ask for payment of the undisputed amount by a date within our payment terms, stating the amount.
5. Offer a short call for anything still open.

For example, a point where the invoice stands might read: "The extra two days in March were approved in your email of [date], which we have attached." That example shows the form only.

The tone should be polite, factual and calm. Do not:
- Concede any item, or offer a discount or credit, beyond what is approved above.
- Threaten late fees, collections or legal action, or mention interest unless the contract provides for it and I have said to include it.
- Suggest the customer is being difficult.

If a point falls under "cannot tell", leave it out of the reply's explanations, list it for me under Part 1 with what to check, and say in the reply that we are checking it and will come back by [date].