We flew from Boston to Atlanta. We arrived “early” there was still a plane at our gate. We waited 45 minutes on the ground until we got to our gate. We were at terminal T and our connecting flight was at terminal B. By the time we got off the plane is was 9:15 PM our flight to Charleston SC was at 9:35 PM. We did our very best to get to the tram and then go to the last gate in the B terminal only to be told that we were too late. This in my opinion was unacceptable. We were waiting on the ground for 45 minutes, Delta should have let the connecting flight know we were on our way. We will never fly Delta again.