What's the harm in going to the callback? Unless you have to PAY for that, in which case I would say RUN AWAY.
See what happens and do some research.
Is it very expensive?
Is this something SHE wants? (I mean REALLY wants?)
Remember, you should never pay an agent except for commission AFTER they get you a job. I know this is a training program, but be careful of scams. Many are willing to take advantage of people who aspire to be a star! And many are legit, too. Just be wary.
PEACE.