Cognizant — Offer letter given but wanted to know whether it is valid or not

I was given an offer letter on 5th of october stating to arrange for the job on 12 th of this month but extended to 14th and asked so many people about the 20, 500 and after the payment gobinath and shrividhya priya were not available to us.
And wanted to know whether offer is valid or not.
And please see to that this should not get repeated for others.
catch them and respond to us