Cognizant — cognizant - selected but still offer letter not released

Hi team (Cognizant interview status - select)
I was interviewed on 8th september 2018 (Chennai, varalakshmi tech park), both technical and hr rounds are completed on same day and hr told they get back with in one week and you will offer letter soon.

After one week i got mail from cognizant that you are selected in the interview process and you will get offer and joining letter soon.