Something really weird happened to one of my pawns

I am playing a French player.

I advanced my pawn two squares putting it next to my opponents pawn.

They then took my pawn which i didn't think they would be able too.

When I asked how they managed to do this then just replied "en passant".

As I don't speak French, I asked them again and got the same answer. After a third request they just replied "en passant", en passant", "en passant" and put me on mute.

Help a confused and bewildered player.

I would just capture his king and say "en passant, game overeau". I think e.p. means "I am French and can make up my own rules." It's sheer arrogance, but no reason to create an international incident.