Very BAD service

My son ordered a whole bunch of parts from them last week to build up his own PC. Delivery was quick and we received the box yesterday. When he open the box last night, the computer box was not included. This morning he phoned them and they now informed him his case is under investigation as it was included in the delivery. My question now is, until when must my son sit with computer parts and no case to install it in for Evetech to investigate what happened. Surely if we were trying to be dishonest, we would not have picked the cheapest part of the whole order to say it was not delivered. I want my son's computer box as we paid for it. How and when someone removed it from his delivery box is not our problem. They used Aramex for delivery and the guy didn't even inform us they were about to deliver. My other son was at the complex gate by mistake when they were about to just leave the box with our security guard.