Cognizant Technology Solutions — joining

Address: Coimbatore, Tamil Nadu, 641305

Hi
I got an offer letter from cognizant, my hr mobile will be not reachable so i can't contact him.. On date of joining i reached out cognizant company but they didn't response... How to i join... I didn't have any response for them and where will i contact for this issue when did i get response for this...
Please help me to how to resolve this issue
Candidate i'd 10876598