There are some situations where you need to cancel your airline ticket. Therefore, air Transat offers you a flight cancellation service where you can apply for cancellation online on their website or go to the air Transat customer service representative.

Before proceeding with a cancellation request, you must be aware of the terms and conditions of Air Transat's cancellation policy, which are mentioned below:
You can request flight cancellation within 24 hours after purchasing the airline ticket and get a full refund of your ticket. But you will receive a refund only if you buy the plane ticket seven days before the departure of the flight. If you cancel the flight ticket more than 24 hours after purchase, you must pay some cancellation fees, which will be deducted from the price of your flight, and the rest will be refunded to your payment source. Non-refundable tickets are subject only to travel credit used for a future purchase with no expiration date, and travel credit will be transferable. If air Transat cancels or delays your airline ticket, you will be compensated without additional charges. They can also provide you with another flight with the same amount immediately after the flight cancellation. If you are requesting cancellation due to an emergency or death in the family, you may request cancellation at any time an airline does not charge you a cancellation fee. You can cancel your airline ticket online through the reservation management section or contact the Air Transat reservations department for flight cancellation.
Does Air Transat have a 24 hour cancellation policy?
If you need to cancel your Air Transat flight ticket, you can request cancellation within 24 hours of purchasing the flight, and Air Transat will not charge any cancellation fees and will refund your payment source in full.
https://www.changebooking.com/blog/air-transat-cancellation-policy