Done...by the time I put the plant in the new pot, I saw it was too small for it. The only available I had that could be used it was too large...as this plant likes large amounts of water and should never dry out, I decided to use it. At least during summer, with HR lower than 20%, it will be ok, I think.
The mix I've used for the medium is bark+10% LECA+20% coco chips+10% perlite+30%sphagnum moss, all mixed.
It almost didn't have any medium in the old pot but it looked like soil but its quantity was less than a soup spoon....all the rest were roots, all healthy (as I was busy repoting, didn't took any photos).
Some photos after repoting: