On the hook

We cannot directly translate this phrase. We need to understand what it means in context.

" Billy was on the hook for a $1200 phone bill. Billy has rich parents, and his parents will flip the bill for him so his credit rating will not suffer"

On the hook means responsibility. If you're on the hook for something, you have some sort of connection to something, and you need to look after it. In this case Billy and his phone bill.

I also used the phrase flip the bill.  I will explain this in the next one.