CMPAustin Hello,
I don’t think that it is a good idea to cancel the ticket. In Italy, you must usually pay a fee of 20% of the price for a cancellation. Some discount tickets are not refundable.
If you have two tickets for different trains, Venice to Milan and Milan to Lugano, you could perhaps cancel only the second one and buy a new one. It depends also on the kind of ticket you have, for an international or a regional train between Milan and Lugano.