Pivot - sorting of report filter

Hey guys,

I have a report that i submit every week which contains several pivots. I have included 1 pivot in the attached file. When additional records are added to the pivot source and even after refreshing, the Customer(All) field is not arranged in alphabetical order. This only works when the pivot is created the first time. All incremental records go one below the other and does not join with the existing records to arrange itself alphabetically. This Customer(All) field is a report filter as shown.

How do i ensure that this field gets sorted each time the pivot is refreshed? I also thought of deleting the pivot and re-creating a new one everytime data is added to the source. However, there are several other pivots and formulae that are connected to this pivot which will get messed up if i delete it.

Appreciate your help.

P.S - I have attached the file and the screenshot of the pivot field that requires sorting.