Cognizant Technology Solutions — HR is not responding after Offer release

Address: Chennai

Hi,

I have received my offer letter on last friday, Its about to start offer acceptance and BGV process, someone from CTS called me and requested to accept the offer, but I didn't got any mail regarding offer acceptance and BGV. So I have informed that person about not getting any mail regarding offer acceptance, he told to contact my recruiting HR, whereas she is not responding for calls and mails from day 1, for HR round also I have called her after document submission. What should I do further? Is there any way to change recruiting HR? More than 10 mails and 10 phone call were made.