If you buy through a travel agency, and you desist on traveling giving notice to the intermediary who sold you your ticket, it must proceed with the refund of the money once the airline makes available the corresponding amount. The agency must ensure official notification to the airline to complete the payment procedure at the scheduled times. If the refund must be made in favor of the agency, because it made the direct payment of the refund or for any other reason (subject to evaluation), you must prepare a signed letter where you authorize Viva Air to disburse the money to the agency, attaching also documents of who authorizes and who receives the money.