Cognizant Associate - Project interview questions

Initially on reaching the venue I had to fill up a registration form.After 1 Hr, I was interviewed by group of two persons . They interviewed for 20 mins .Questions were based on scenarios and basic Cognos knowledge. They also asked some SQL questions.After technical interview I has to go through HR round where I had to fill up another form with all education details,present employment details and expected salary.After 2 weeks got a call from HR with the offer.After accepting the offer over the call they mailed me the offer letter within 2 days.

I have attended the interview on 17th May 2014, I cleared the Technical rounds on the same day ,the HR told me that I am selected and the HR round will be over phone and that they will be calling in the coming week , but it has been almost 3 weeks now and there are no signs of the interview also they are not responding for the emails. Can i have any hopes on this or should i consider this as no result and continue my job search.?