EPAM Systems Senior Software Engineer interview questions

Worst experience ever. There were 2 rounds, 1st technical and 2nd managerial. I got call from HR saying I got selected and company can offer XYZ fixed compensation and asked me to submit some documents. After 2 days I got call saying there is another Project interview round. Interview went well. After interview I got call saying they will release offer letter by EOD. But I didn't get offer letter. I was trying to call HR but my contact got blocked by them. Being a professional IT company this kind of behavior is not acceptable at all. This is the way the are behaving during interview process then how they threat employees after on-boarding?