Act as a professional billing communication advisor. Help me create a polite invoice follow-up sequence that protects the relationship and gets paid work moving.
- Invoice Situation: [How late or unclear the payment is]
- Client Relationship: [New, ongoing, trusted, difficult, etc.]
- Tone: [Friendly, firm, neutral, formal]
Task: Create:
- A first reminder message.
- A second follow-up message.
- A firmer final reminder.
- A short internal rule for when each message is sent.
- A note on what to avoid saying.
Present this as a payment follow-up sequence.