What happens when I use Minecraft Alts?

I know Minecraft Alts violate the EULA. But what does Mojang do about it? Can I already be charged for using it? Or is the old just banned?

Then nothing happens.

I very much doubt that Microsoft will act legally haha ^^

Nothing happens at all. I used alts myself for months.

But what does Mojang do about it?

Nothing at all

Can I already be charged for using it?

No. You are only violating the terms and conditions. There's no charge. But they can delete your accounts with no right to a refund.

Or is the old just banned?

Nope, Mojang doesn't ban accounts.

If the terms and conditions are violated, you will not be displayed.

For this you will usually be banned.It can also happen that your game is no longer usable because your game is blocked or that your PC is blocked, e.g. For online functions.

Can my main account (which I officially purchased) be drawn into this?

Theoretically yes. You should also delete your main account for this.

Practically: No. They have better things to do than chase you.