Wrong stamps on a letter

Today I did receive a nice minisheet with "personalized" stamps. (Not so because they were issued by PostNL, but nice.  As you see a lot here the stamps used on the cover are old. Do receive also stamps from Italie, Swiss and Denmark with that stamps, or combinations old and new. These stamps are not allowed on Dutch mail. They are for the International Court of Justice, but who with PostNL will know that? Maybe its time to stop with the Guilderstamps, PostNL likes that. They "steal" over  € 50.000.000 from the people with this action. So not everyone is happy, looks like a govnerment with taxes....