I guess I'd call it "changeLastName". That's closer to the domain, we don't go to the Department of Births, Deaths and Marriage and tell the clerk we want to "set" our last name. But that is being too pedantic, even for me.
I'll concede defeat. That is a pretty good example. At the end of the day, "customer details" class is actually a big bag of fields that needs some access control and validation.