One of my ex staff went to a British Gas customer service advisor interview and it was quite a session, she has to go through a role play where she had a difficult client who was complaining and she had to be calm and collected. Her role was to try to make the caller feel confident that they were getting the right deal for their energy, but there will be targets to hit and so you need to mention that you are target driven. When you first meet the interviewer, step towards them and shake their hand saying your name clearly and with a smile, you have to be positive and cinfident and speak clearly, as this will be a phone based role. the key thing will be to listen to the questions you are asked. When they ask you if you have any questions, you should ask soemnthing about progression in the company.