Colan Infotech NET Technical Lead interview questions

Colan infotech conducted walk in interview in Bangalore. They interviewed me 3 rounds and selected. And also they asked me to attend client interview. That also got cleared. They said they will send offer letter. After that they said HR is on leave once he is back they will send offer letter. Its been a month still there is no response from them. HR is not responding to calls. If they dont wanted to offer, why they waste candidates time by taking 3-4 rounds of interview and promise that they will send offer letter and ask candidates to send the personal documents. Please stop wasting candidates time if you cant offer.