You should have an email confirmation of your reservation. That should tell you the conditions of your booking and should be dispositive. You either booked a prepaid rate or not and that email confirmation will say so.
If you booked a prepaid rate, you have your answer. It's what you booked. If you did not, you have your proof.
Your reference to a 50% refund is unclear. Are they offering you $450 now which you will then pay when you arrive or are they offering you the room for $150/night?