Why do you want to change those column names?
As you know doubt know, the main use Pivot Tables is not for final presentation, but to conduct analysis "on the fly" and vary that analysis easily. The ( ) in the column names adds useful information.
If you need to make a nice presentation of the results to show others, then start a new table, select the cells in the Pivot Table, and copy/paste into the new table, where you can edit the column names and other aspects of the appearance to suit your needs.
The time it takes to do that usually is far less than the time you have saved by using a Pivot Table to analyze your data instead of inputing and debugging formulas.
SG