. Nowhere in Confluence of BLKN is stated that booking two segments at once from MAT is mandatory. In that case agent Maria Decheva decided it was better to book GDS first. In latest updates on Vueling, trying to refund the reservation is nearly impossible. From MMB in web you have to provide a very good reason to cancel the flight (death, COVID etc.) and after that Vueling wants documents for evidence. When you try to call the A/L there is an automatic messages "press one for English, etc." which doesn't lead you to a live agent. In Confluence - article - OP Create reservation per segment (Bookie) there is no rule for booking everything at once even if the flights have GP or is from GDS. There is only Secondary recommendation to book from least expensive to most expensive which our agent Maria decided to follow., text, logo, wordmark, writing, heading, signature