Bag checked in

I paid for my 20kg bag check in on the 5th is was 155, and 310 in total when I include the return flight. When I got the airport the next day they said I don’t pay for the checked in bag, I had to pay again just do I don’t miss my flight, today I’m checking in and I see there is still no checked- in bag added to my flight. I’m leaving tomorrow morning and I don’t want this stress please fix it.