If you qualify for the interview they will give you a short call to hear your voice and level of English, asking a couple of questions about yourself. If everything is ok they will invite you for face-to-face interview and will ask you to make a test call to a "client"(manager who will be sitting in another room) to hear and evaluate your voice, so try to sound loud and clear in order to succeed. They will give you a script , so there is no need to prepare your own, even though they might ask you to prepare one beforehand. Overall the interview process is not tough at all.