received empty box from dpd

I placed an order for an iphone 7, which was due to be delivered today. I received the order, the delivery man made me sign before giving me the box it felt rather light. I then opened it to see that my iphone 7 was not inside. No iphone box, no phone no nothing, just a brown box that it was used to deliver it with. I called the delivery company and they say i have to ring apple. I rang apple and they said they would proceed to a shipment investigation. They asked if I would prefer a refund or replacement , I said refund because I cant bare to go through getting an empty box again.

Is it definate that I will receive my refund, because, I feel if someone has stolen the phone who will admit too it.

£700 for an empty box.