I received an invitation on Upwork to apply to a job for HR assistant. After that, they contacted me on email and set up an interview. It was a text/chat interview. I just got an email saying that i'm hired and that I have to sign some documents. The fact that's telling me this is a scam is that they want me to buy some software worth $300 and after that they will reimburse you. Also, their email is @usa.com and they were new to Upwork. The person I talked to pretends his Jeff Dobbs Vice President, Human Resources\ What should I do to find out if this is a scamp?