Partners Group - Client Facing Role

I’m interviewing for a client service role and I’m preparing for an interview.
Any tips ?! How to be ready ?
It’s exactly what I do at my current role, how do I ace it ?
Also I’m not sure why on this forum people consider it a middle / back office role whereas at my current company it’s considered a front office role !
How can I answer their question on why I wanna move there. Nevertheless it’s the same role I’m having now ?!
What excuse / answer can I give ?