Hello,
The current version of the replaceChartData method updates the DOCX values but not the XLSX values. So if you edit the values of the chart, the old values replace the data.
You could use the addChart method with a WordFragment to add an editable chart to a document created from scratch or using a template.
Updating the XLSX is a work in progress and it's in beta stage; if you want to test the beta version of the replaceChartData method, please send to contact[at]phpdocx.com if you are using the classic or namespaces package and the DOCX with the chart you are trying to replace and we'll send you the new file and a script to illustrate how to use it.
Regards.