Hola Janis
As we mention in our FAQ pages, Kwiziq currently focuses on Peninsular Spanish and there is testing on the vosotros form and we encourage students to learn this form because its always useful to know more. However, in the future we plan to widen our scope so that you can select which type of Spanish you learn. For the moment though, there is no way we can "turn off" vosotros.
Here are some links with more information:
Saludos
Shui