Job ghosting MNCs

I could see some companies are simply ghosting jobs. I have faced the similar situation in Cognizant, persistent, Synechron and Wissen. Get final round of discussion feedback as positive and then HR will not reply you through email or phone. They do not release offer letters.

After following up the HR for a week, new HR from same organisation will call you again for first round.

I doubt if these companies are releasing offer letters or they are job ghosting. Is there anyone really getting onboard?