Do you mean ticket or do you mean reservation? In any case you need to get back to the office that issued whatever you have. This is a community help forum so we can give advice but can’t change things for you!

If you still want to use the same train but just board in Milano Centrale instead of Milano Rogoredo, then I wouldn't bother. The price of a pass reservation stays the same and there's just a small chance that your seat is still occupied by someone else leaving at Rogoredo.

thank you, 

that mean i can take the train at the Milano centrale without chane departure station?

If the train you booked on stops there yes :) 

Not all trains stops in Milano Centrale ;) 

BUT: there are gates at Milano Centr-but I dk how strict they check (only went out myself a few weeks ago). Not all trains start at Centrale and then stop in Rog: you have to check that. If it does not work: a metro ticket there good for the whole city is only 1,50 or 1,60 or the like.

The train mentioned stops at Centrale, as you could have checked yourself.

The checks at Milano Centrale are not strict at all. Sometimes it's enough to wave with a reservation or your pass.