Cognizant Technology Solutions — Not received offer letter

I have given an interview for CTS on November 16.. after that I got a mail saying I have cleared the interview.. hr called me and said the same.. after a couple of days I got a mail requesting for documents like Adhar, Pan, 3 months payslips, updated resume and they sent Candidate information sheet to fill frand I have sent all doccuments.. I got a hr call on Nov 29 for negotiations.. everything went fine . On Dec 4 I got a mail regarding live session. but till now I haven’t recieved my offer letter. So requesting you to please look into this.