Cognizant Technology Solutions — joining letter not released

Address: Ahmednagar, Maharashtra, 414106

Cognizant — joining letter

Hi cts team (Cognizant interview status)
I was interviewed on 21st july 2018 (Hinjawadi, pune) through amcat both technical and hr rounds are completed.

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.

After that on 3rd september, i have received offer letter n pre - joining formalities mail. I had completed all processes n on 3rd october i received mail for reminding the acceptance of offer letter and mention that "tentative date of joining is october".

But till date, there is no any mail received.
I also sent couple of mails and but no reply from cts team.
Is anyone give interview on same day through amcat.??? If yes then please told mi what should i do.?