The process was very very simple and easy. After saying hello, the HR said:" I don't want to waste your time. I just realized that the hiring manager is not hiring F-1 OPT status candidates. I'll need to check with him again. " I said fine. After a day, I followed up, he said manager confirmed not hiring foreigners. So, my advice, if you got an interview from them and you are a foreigner, don't be happy too early. There may not be a chance to present yourself.