is there any way to change a train to a later time

It depends entirely on the tickets you purchased. If it was full fare, then yes, you probably can, if it was a highly discounted advance purchase, then probably not. Check the terms of the purchase.

Where/how were original tickets purchased?

Here is a quote from the Trenitalia site:

"If you no longer intend to make the journey as stated on the ticket you bought, you can request a ticket change (only once from the day of purchase and until one hour after the booked train's departure) according to:
• type of ticket,
• number of persons travelling,
• route,
• departure/arrival stations,
• train category,
• service used,
• class,
you can make ticket changes (paying any price difference) before departure at any ticket desk and authorised travel agency.
After departure, only at the ticket desk in the departure station of the train indicated on the ticket."

Thanks for the imput. The tickets were purchased through RailEurope and I don't think there was any discount involved- at least not on my end! Grazie

I just read the ticket envelope from RailEurope and most of it applies to Eurailpasses but the slip next to the ticket said that 80% refunds before 3 days are available if unused nothing about changes. It also said that these changes have to be made at the issuing office. Am I out of luck?

Call RailEurope. That is the best way to find out, since they issued the tickets.