Create one file for the trip. Save the original offer as a PDF, export or screenshot relevant booking pages and keep the confirmation, invoice, contractual terms and payment records. Add the date and time of receipt to every later notice.
For an electronic message, retain sender, recipient, subject, attachment and the complete text. A customer-account notice may additionally be documented by a dated screenshot. After a telephone call, record the person, time, substance and any promised written confirmation. The tour operator entry in the glossary can help identify the role of the businesses involved.
Prepare a short chronology: booking, first information, conclusion, proposed change, receipt, response period, your response and the later reaction. Separate a price increase, a service change and a purely organisational notice. That distinction prevents an essential amendment from being confused with ordinary travel information.