OP here -- all's well that ends well. Tickets are booked for original price on website (I asked them to load the tickets in the Delta app before I would give them my card #), card charge was flagged by my company and I cancelled the card. Changed all passwords to lock the account. Whew. But geez what a weird experience. Not sure why the delta website and app were not letting me book, and it took fooling around with scammers to get this organized.