I'm not sure what the questions will be but you'll need a good clear voice, a pleasent manner and endless patience. Patience with people who don't undertsand, with people who are rude, with people who think they know it all etc etc. And the patience to repeat the same conversation over and over again all day. You'll also need to learn the software and show that you can achieve a reasonable speed along with accuracy. Oh, and you'll need to be able to sell products as you'll have targets for "upselling" ie. if I call for car insurance or membership, you'll be wanting to sell me house insurance.
Not much you can do to prepare except to be yourself and as cheerful and enthusiastic as possible. Good luck.