Promo rules are strict because the fare was cheap. The trouble starts when the confirmation email is a template in Malay that was written for a flexible fare two years ago, and the manage-booking screen is a newer English room that states “changes not permitted after 24 hours.”
A booker in Kuching reads the email. A relative in Petaling Jaya opens the app in English. They argue with each other before they argue with you. The hotline then spends twenty minutes proving which sentence is the rule.
Priya keeps both languages on the desk when she writes a cancellation brief. She does not translate. She checks whether the refund window, the change fee, and the no-show rule occupy the same hours in both. If they do not, the briefing names the pair of sentences, not a theory of localisation.
If you only proof the English screen, you have proofed half the ticket.