Is the rifle new or secondhand? If new take it back at try a chamber gauge and see if it chambers, if not, well they messed up and will sort it out.
If used borrow a chamber gauge and try it, if it doesent chamber you now why its second hand.
But the easyest is still to pull a bullet, full size it and check if it fitts, the guy that called the round new could always mean they bought it new from a reloading company.

But most important, how does it look? picture?