Travel booking sites must suit Copa Airlines cancellation policy to sell tickets on behalf of the airline. If you book a visit on one of these sites then have to change or cancel it, you'll probably get to charge the airline for these charges. Also, usually, they do not offer refunds. The utmost value which will be obtained may be a voucher that uses the ticket value at a later date and typically specifies that the voucher must be used within one year of the first travel date.