Actually, it's very easy to change or edit Pivot Chart's axis and legends within the Filed List in Excel. And you can do as follows:

Step 1: Select the Pivot Chart that you want to change its axis and legends, and then show Filed List pane with clicking the Filed List button on the Analyze tab.

Note: By default, the Field List pane will be opened when clicking the pivot chart.

Step 2: Go to the Axis (Categories) section or Legend (Series) section in the Filed List pane, drag all fields out of the Field List pane.
Then you will see all axes or legends are removed from the Pivot Chart.

Step 3: Now go to the Choose fields to add to report section in the Field List pane, drag the filed to the Axis (Categories) section or Legend (Series) section.

Note: You can also right click the field and select Add to Axis Fields (Categories) or Add to Legend Fields (Series) from right-clicking menu.

If you want to change the data source of a Pivot Chart in Excel, you have to break the link between this Pivot Chart and its source data of Pivot Table, and then add a data source for it. And you can do as follows:

Step 1: Select the Pivot Chart you will change its data source, and cut it with pressing the Ctrl + X keys simultaneously.

Step 2: Create a new workbook with pressing the Ctrl + N keys at the same time, and then paste the cut Pivot Chart into this new workbook with pressing Ctrl + V keys at the same time.

Step 3: Now cut the Pivot Chart from the new workbook, and then paste it into the original workbook.

Step 4: Right click the pasted Pivot Chart in the original workbook, and select the Select Data from right-clicking menu.

Step 5: In the throwing out Select Data Source dialog box, put cursor into the Chart data range box, and then select the new source data in your workbook, and click the OK button.

Till now, the Pivot Chart's data source have been changed already.