Did you already enter beltegoed on the number?
The internet works fine.
Via 4G? Internet via wifi doesn't require a simcard at all.
Welcome to the community @Christiaan12345. Like Peter I'm also curious how you use the internet connection. If it is via Wifi, it is not related to your prepaid credit. How exactly is it blocked? Did you get a message telling you it is blocked, or has something else happened?
Have you called *101# yet? That way you can see the remaining credit. If there is none, you're not blocked, you just need to top it up.