Cognizant — offer letter receival

Address: Chennai, Tamil Nadu

I attended cts interview on 23rd sept 2018, thoraipakkam, chennai. Cleared 2 tech rounds and then attended hr. Filled up the required form and had salary discussion. They saif they ll mail me after a week. I got a mail regarding uploading of document with photo attached, which i did the very next day. Few days later i received the auto generated congrats mail from tag that i have cleared the rounds and they will shortly release my offer letter. Its been over 3 weeks and i m still waiting fpr the letter. I need someone to hel me out here.