I always contact chat to do this because the website is buggy and always shows 100% of the fare as cancellation fees on my end. If it's within 24 hours, you should get the money back to your credit card, else it's a voucher assuming your flight is 7+ days away.

Some other things to be aware of if you go the travel voucher route - I received a voucher for cancelling a 2-person itinerary. The email with the voucher said I could use it on multiple itineraries for either one of us until the full value was used. Thought I'd book some tickets while I was at the airport (paid $220 instead of $390) and the agent said the voucher we had was single use for itineraries that had both of us. I insisted she try the code anyway, and it worked across multiple itineraries that had both of us on it, but not on any single person itineraries.... kind of a situation where neither the email was entirely right nor the agent.