Casting for voices is rather rare. But production companies are always on the lookout for the right voice. Make an account on Soundcloud first, upload your self made recordings (you can do this with a laptop or smartphone in a quiet environment) en send in a link to a production company.
If you first want to discover your voice and fine-tune your timbre, take a look at this overview of voice coaches.
Are there any Belgium-based casting agencies you believe are missing from this page?
Agencies: Voice Acting
how to put yourself on the market
01 - preparation
what do you stand for, and what do you need to profile yourself?
02 - registration
agencies will hopefully include you in their portfolio and promote you
03 - follow-up
brand awareness and brand connotation will help you get recognized