Customer service is stuck in a loop!

I've been waiting almost a week for the rest of an order to arrive. The parcel that had my sticker on it had someone else's order and packing slip. After a week of different people "escalating" it, I still don't have an answer as to when I'll receive the rest of my order. It's ridiculous at this stage. I keep having to phone them, no-one calls me back and my last phone call was almost 18 minutes of me holding. o***