Indigo Airlines — Flight ticket refun/rearranging dates

My husband accidentally booked the wrong dates for our February 2026 ticket to India through Indigo Airlines. As soon as I received the itinerary, I realized the mistake and requested a refund or a date change. However, they are asking for £200 to reschedule, which has disappointed me. I kindly request that you consider my situation and provide a refund or rearrange the ticket without the £200 charge