Yup, we all know that in an ideal world everyone in aviation - and lots of other businesses too - spoke the same language, whether it's English or whatever. But it's not an ideal world. And it's kinda easy for us native English speakers to expect everyone to speak our language.
Pilots tell ATC that they want to change their plans every day - maybe a change of destination is unusual, but it's not unheard of by any means. Of course the French controller passed on what he thought you wanted - what do you expect him to do? Do you really want controllers to double-check all your flightplan details every time you change sector?
You had a bad experience. It's unfortunate. But how you deal with it is about being professional.
And everyone has to recognise that it's not a perfect world and be alert to potential misunderstandings. Chalk yesterday up to experience and learn from it. Because sadly, in 30 years when you are showing the ropes to someone else who is new to commercial flying, there will be similar things that happen - perhaps not language issues, but something! It's just life.