Tachyon Technologies Software Engineer interview questions

There were 2 rounds of interviews for their client company, after clearing the rounds, they send me the offer letter and told me to join immediately. They convinced me to drop my resignation from my current company. But 2 weeks after sending the offer letter they told me the client has changed the joining so they want my current company to take me back or asked me to try for other interviews. It was devastating. Tachyon offered a good package but you can't trust them, they have zero ethics