Use one earpiece

Hello!

I just got my new Airfun free pro and so far I love them, but I couldn't find how to use one earphone and not the two of them. I put only the left one and I tried to use it for the ambient mode, but it didn't work. So when I put the two together suddenly it did work, and when I put the right one back in the case the left piece went back to normal mode.

anyone know how to use it for one piece? 

thank you!