Cancellation of any activities is based on the cancellation policy stated on the voucher. If it is feasible and there is availability in the new activity that you want, you can go ahead and change the same(additional costs may apply).
You can reach out to us. We are available from 10am IST to 7pm IST(weekdays). In times when we are not available you will be able to reach our local partners or the direct activity provider mentioned in the voucher.
It is always best to get in touch with the airline people directly to get a quick solution. You can also reach out to us through the website.
You can either lodge a police complaint or call up the embassy to figure out a solution.