This is called a guarantee booking, or a " GTY booking". What category did you book into?
Do you know anything about insides on HAL? I assume you took the GTY booking because it was cheaper, right?
Yes, it's possible you could end up in the smallest, lowest level inside cabin. You consented to that when you accepted the booking option. If you booked a higher level inside GTY, you won't end up in the cheapest inside.