How i change audio movies "Dual Audio"

I have some films with audio dual and I would like to know as I I change the audio one of a film?
I have a BD Sony BDP-S470, use the SERVIIO as serving DLNA. The Archives of video mkv possess two languages of audio, English and Portuguese, but the films are shown only in English. Using the keyboard key of the remote control to change the audio one, option of audio does not exist second. What I must make to see films in Portuguese?
Tanks!
Marcus Cesar - Brazil - mca.marcus@ pop.com.br

[Illico]

For the moment with Serviio, when files are transcoded, only the first audio track is used, you could use TsMuxer tools or Mkvmerge to remux the Portuguese track in the first position.

When file is delivered in native format, this is the renderer that must select the proper audio track, not sure Sony BDP-S470 supports that on MKV, I have to check...