You only have a few choices when changing your flight with Turkish Airlines. You can connect them by phone or going to one of their offices in your city or country. You can change your flight online if you bought your ticket directly from Turkish Airlines.
https://flightcancellationpoli....cy.com/turkish-airli

Vistara Airlines offers a very simple cancellation procedure, so if you need to cancel your flight for whatever reason, you can easily cancel your ticket. Vistara Airlines does not apply cancellation charges if you cancel your reservation within the first 24 hours of booking. If you cancel your Vistara ticket after 24 hours of booking, the airline will charge you under the Vistara Airlines cancellation Rule.
https://flightcancellationpoli....cy.com/vistara-airli

The Swiss Airlines flight change guidelines allow you to make changes to your travel ticket, such as a name change, a rescheduled flight, or a seat upgrade. If you miss your flight due to any circumstances, Swiss Airlines' flight change policy allows you to change your flight. If you change your flight within the first day of booking, the airline will not charge you a flight change fee.
https://flightcancellationpoli....cy.com/swiss-airline