Optum Custimer Service Representative interview questions

The initial interview was easy. Then after that is the mock call where I failed because it is my first time to be interviewed by employer. And I didn't make it to the final interview.

The interviewer that was assigned to me was a bit rude. He is a guy, I forgot his name. I felt I was so stupid in answering all the questions. He asked so fast and I felt hurried. Not a good motivator. Maybe he just strained the good English communicator but not the struggling one. The question is quite easy but when you're struggling you really cannot move to the next phase.