Once you purchase a ticket through a third party like Travelocity, Orbitz, Expedia or a travel agent, you will need to work with them regarding a refund on the ticket price.  You can contact the airline directly, but chances are, they will refer you back to where you purchased the ticket.

Yapta does not support third-party websites.  But from what we've heard, obtaining a voucher or credit on a ticket purchased through a third-party may prove difficult.