Artech L.L.C. Android Developer interview questions

Taken 1st round as technical round. It's a little bit difficulty but we can able to clear. After got the selected mail, took more time for document verification. Finally, they told me to release offer after 3 weeks of background and document verification. As they told within 2days will release an offer letter but didn't get any release offer letter mail. After three days, I reached them via mail, phone call, sms but no response. I tried multiple times didn't get any response from them. Finally I got total disappointment 😞