I am wondering, is it a folder or a Data File he wants to change the name of? If it's a data file, the group of folders that contains the data for an entire email address, the actions are a little bit different. In that case you'll have to go to account settings for that email address, and you can change the name there. 

This may not be this person's problem, and, if not, I'm sorry. I've actually had someone come to me with the same problem while calling it a folder before, so I thought I would throw it out there.