Some alternative dispute resolution (ADR) bodies accept complaints in English. But if a complaint is written in English and you also supplement a French or Dutch translation (as a courtesy), they will often follow the procedure corresponding to the translation that you give, not English. So if you really want the response in English, obviously giving a translation can screw that up. I have not tested whether you can provide a translation but then explicitly state that you request an English procedure.

Interesting gotcha: if the website has an English version, you cannot trust that. They may even have the rules of procedure written in English -- but then submission rules still limit complaints to fr/nl/de. So it’s important to read the rules of procedure and see what languages are accepted.

If a complaint form is provided in English, things get weird. Although I have never seen a PDF form in English where English was ineligible, I think I have encountered cases where a web form was in English but the rules of procedure exclude English. I paid no attention and wrote English, and it was still accepted contrary to the rules of procedure.