Cognizant Technology Solutions — cts - offer letter not received

Address: Kolkata, West Bengal

I have given technical interview on 13th jan, 2018 and hr round 19th jan, 2018 for java developer at kolkata, west bengal.
During hr round hr told me i will be getting offer letter within a week. Still i didn't got the offer letter every time they are saying it is under process. In10th march, 2018 they called me and told my tagged project is having some billing problem, so they are tagging me to another project and i need to attend another interview on 17th march, 2018. But they didn't send the interview call letter and now they are not responding to my mail also.