Umm, I mistake pointed. CSV output by receipt.php sorry.
So, represent questions.

What charset recieved CSV file from eguide module?
Is that file charset UTF-8 or NOT?

If that is UTF-8, check your reading tool for CSV.
Another charset has come, You need check your PHP setting.
You can check put "info.php" file and view by web browser.

Checking which to use, "mbstring" or "iconv".
And check converting condition if you can understand program.
(receipt.php line 140-)