Act in this order so nothing else leaves while you fix data.
- Open the debtor and stop or pause chasing for them (never-chase / stop controls on the debtor record, or pause the active invoices).
- If many messages might leave, consider the account kill switch until the list is clean.
- Edit the contact email/phone to the right person. Archive obsolete contacts rather than leaving stale addresses active.
- Add an internal note of what happened and when.
- Review Activity for what already sent; do not pretend it did not.
Responsibility
PayBlah sends reminders as your business. You are responsible for content and who you contact. That is why contact hygiene matters more than any template tweak.
If they asked to stop
Honor stop requests in Activity / on the debtor. Stopping means stopping — do not re-enable casually.