Different info from website and phoning?

I checked the website for an update on my parcel, and jt said it'd been delayed but without and clear info on when it'd be delivered. I called and got the automated system that said the parcel had been delivered (definitely hasn't, ive been in all day). I pressed 1 and gave my details to raise an investigation, but I'm quite worried as the item being delivered is a one of a kind item - it can't be replaced if its lost or stolen. Any advice?