Originally Posted by WineCountryUA

Yes but probably best to have an agent do it, Don't be concerned of needing a reason, you don't. And there are many reasons to want to do this.

You can do this yourself by going to change flight. At some point you will be ask to which passenger you want to make the change. Continue selecting a new flight BUt don't confirm the change. The PNR will have been split with no changes. But really safer to get an agent to do this.