Trip.com Charged for Checked Baggage but Ticket Shows Cabin-Only

I purchased a flight ticket from Trip.com, paying extra for 20kg checked baggage plus a cabin bag. However, after receiving my ticket, it showed only cabin baggage included. When I contacted the airline, they confirmed that my ticket does not include checked baggage, even though I paid for it through Trip.com.

My flight is a round trip with layovers, meaning I will have to pay additional baggage fees at each leg of the journey. If Trip.com charges for baggage upfront, why is it not reflected in my ticket? This is misleading, and I demand an immediate resolution and a refund for the baggage fee I was wrongfully charged.