Is this job as it seems?

I recently was offered a position to be a Graduate PPI claims handler for a business which is under the umbrella of a large bank. All I did for the role was complete a short 10 minute phone interview and then head into the recruitment centre to fill out my details and give them info to do background checks. After doing more research on the position, the starting pay is around 29k rising to 34k after probation. This seems a large amount of money for me as a starting salary alongside the fact that all I did was a short phone interview.

Another aspect which seems odd to me is the fact that I seem to get paid by either setting up my own limited company or using a provided umbrella company, what does this mean and why do they do it?

Hope you guys can help me out because this seems like a good position although can't help but think there is a catch.

Cheers.