Tech Mahindra Software Developer interview questions

I was called by tech mahindra and set up interview on webex. After that HR email me saying congratulation and they need my information for background check.He sent me offer letter with joining date and said to not sign it because joining date may vary depending on background check.They took 1 month for background check and drug test.After that He email me saying that background check is all done and I have to join from next monday & He will send me revised Offer letter tomorrow. I left my current job and ready to move at their client location.From Next day HR stops replying emails and calls.After 2 days he emailed that may be there is change in project and joining date may vary and He will let me know in 2 days.I used to email him everyday but He never replied.after couple of days he emailed me that may be that project will never starts and If they have any opportunity for me they will let me know.Totally he changes my joining date 5 times. HR was not responsive at all.