Cognizant — not release offer letter

I gave interview on 15th dec'18 in cognizant. I cleared every round in interview including hr. At the of hr round they said, you will receive offer letter within two weeks. Its more than two weeks. I didn't receive a mail from their side.
I don't have hr contact no to contact.
Kindly suggest me what to do next.
Anyone having hr details, kindly let me know.