Hello Azra. The airfares the airlines nowadays offer are 80% non refundable and not changeable and about 20% you may be able to change, but only against extra cost.
This service is not offered online. Each airline has different costs and hundreds of different rules. If you need to cancel or change your ticket, you have to contact customer our support for assistance: http://support.sky-tours.com On of our friendly Travel Agents will than assist you to find the best solution for your needs kind regards Willy.