Cognizant — Didn't get offer letter

Hi

I am Kajal Rathi.
I have completed my HR round. HR confirmed that he will be releasing an offer letter till 13-14th Dec, 2021, but still I haven't got my offer letter and also no updates. Phone number is switched off from which I got call and discussed CTC, designation, etc. and one HR is not responding.
Please help me in getting the offer letter.

Thanks in advance