No phones in cabins, not a lot otherwise on this SHIP? Do as Miller, Hamstreet suggests and speak to your cabin stewardess. Otherwise book on a different ship.
You can contact your cabin stewardess who will make the necessary arrangements. It can be slow but you get there in the end.
Shout loudly down the corridor?
I presume room service would need to be prebooked from receiption or a note left outside your cabin for room service.