Make room for the other version
Ask what the other person understood before assuming that you are arguing about the same facts. For a message about how to apologize for changing a travel itinerary, use this factual base: confirm the booking, timing, guest, transport, or budget change and who now has to adjust.
Correct the record precisely
Correct only what you can support, acknowledge any real impact, and propose a practical way to prevent repetition. Offer a replacement plan, reimbursement, or clear decision before the next real deadline. Make the immediate next step clear enough that the recipient can answer without reconstructing the entire history.
Agree on a testable next step
Do not minimize lost money or time, and do not invite extra people into a plan without consent. Follow venue, transport, insurance, and local safety rules when an emergency or stranded traveler is involved. Do not recruit an audience, publish private evidence, or turn a misunderstanding into a campaign about character.