I would not bother going, it is not worth it
Be punctual and dress formally. Make sure that you're familiar with your CV and can answer questions on it. The sort of questions that you might expect to have to answer are the usual: "Can you name a time that you've resolved a difficult situation for a customer?" "Name a time you provided exceptional customer service." That sort of thing. If you can familiarise yourself with the way credit cards work in terms of interest and repayments, you're onto a winner.
Obviously, if you need money, then go for it because it's good pay for young people and/or summer jobs for student. Otherwise, don't.
Dont mention that you have applied to any other jobs
Research company and try to understand their product and the role you are applying for.