Hey there Robert,
Welcome to planDisney and thanks so much for stopping by!
The best way to get a name change on a
ticket you've purchased, you'll want to
call the Tickets line to speak with a Cast Member. They will be able to pull up the details about your tickets and let you know what options you might have - like getting the name changed on a ticket.
I'll note that the name change is only able to be done for wholly unused tickets. If the ticket has already been used by someone then it is already locked in to that person and is not able to be used by someone else.
Additionally, if helpful, the names that you write in for tickets when you purchase them are more used to help you keep them organized. Again, if a ticket is unused and a ticket had a name of a party member who is no longer to join you in the parks then a new party member can use that ticket instead without making a name change. The first time the ticket is scanned to enter a park is when it gets assigned to a Guests and thereafter needs to be used by that same person but it is not determined by the name on the ticket.
I hope that helps, Robert! Thanks again for your question and have a wonderful time on your upcoming visit to the Happiest Place on Earth.
Have a Magical Day,
Greg