In my judgement, Delta must have taken the cheap route in choosing an Indian call center or a training budget. As others have said, the knowledge level is incredibly low (e.g., not knowing which fares are upgradeable). United also uses Indian call centers and I've found their people to be of much higher quality than those at Delta. Outside the airline industry, I use an HP computer and their night time calls go to India and the level of service is truly excellent, with their people often calling the next day to find out if their "fix" was successful.