all idrive have basic Voice recognition (but it is rubbish) i.e you can laboriously save contacts and numbers etc.
There is a voice command option, which offers much greate voice command interaction, so i may be you only have the fist "standard" voice control, not the upgraded voice command option.
that may explain why you are having limited sucess.
If you have the Full voice setup, then it may not be working... you will need to check the options fitted to the car on the original build sheet to confirm if you have the voice option fitted