Write a payment reminder email for an overdue invoice:

- **Customer name:** [First name or "Valued Customer"]
- **Invoice amount:** [$XXX]
- **Days overdue:** [7 days / 14 days / 30 days / 60+ days]
- **Escalation level:** [friendly reminder / firm notice / final notice before collections]
- **Payment options accepted:** [check / ACH / credit card / online portal]
- **Contact for questions:** [phone number or email]

**Tone guidance by escalation level:**
- Friendly reminder: assume it's an oversight, warm tone, no consequences mentioned
- Firm notice: professional, direct, mention a follow-up date
- Final notice: serious, clear consequences stated, specific deadline given

Keep the email concise — under 150 words. Include the invoice number if possible.
Overdue Payment Reminder
