EPPlus Font Family Not Affected

Try this:

var allCells = sheet.Cells[1, 1, sheet.Dimension.End.Row, sheet.Dimension.End.Column];
var cellFont = allCells.Style.Font;
cellFont.SetFromFont(new Font("Times New Roman", 12));
cellFont.Bold = true;
cellFont.Italic = true;

This issue occurs because EPPlus (version 4.5.3.2) does not support Font Charset. Font Charset for the selected Font ('B Zar') is ARABIC (=178). I have forked the EPPlus on the url https://github.com/mzatkhahi/EPPlus and fixed this bug. Then you can use this code to support the persian font:

workSheet.Cells[1, col].Style.Font.Charset = 178;

workSheet.Cells.Style.Font.Name = "Arial Narrow";
workSheet.Cells.Style.Font.Size = 10;

This will affect all rows and columns.