Sort cell content alphabetically

As Graham mentioned, the sort A-Z does need to be refreshed. However once this has been done you can still move an item up or down the list. So if you have an "N/A" you can always move it back up to the top. 

Generally they are in alphabetical order. If they are custom fields they are in the order of the list, which the user can set to sort A-Z. They just need to refresh that sort if they add a new item to the list