It is necessary to set black and white printing in the printer properties - the settings in the pdf browser window (the Print in shades of gray (black and white) option does not work correctly! This option only converts to grayscale, however, if color printing is set in the printer properties, the printer can use color toners for more shade credibility — printing is then billed as color.
Properties can be changed also after the print job was sent to server at https://innet.vsb.cz/en/user-account/service-account/
You need to click on the pencil icon for each print job and make the necessary settings. In addition to black and white printing duplex printing can also be set.