Parcel not delivered as promised

I had my car spare key sent from Eastern Cape to Johannesburg on 03/12/2015 using an overnight service meant to take 24-48 hours max and for 3 days I could not track the parcel using the way bill number provided. I decided to call the head office to assist in tracking the parcel, still the parcel could not be tracked. Called the branch which it was sent from, I was told the parcel was left behind when they came for the pickup and it was only sent out on 8th and i will get it on 10th. My parcel was not delivered on the promised date and I called the branch again to trace it for me and I was told it's out for delivery and it will be delivered today. Still no key and I have to a trip to KZN tomorrow morning. I opted for the overnight service because it was supposed to be the fastest, I knew I would need the key by Friday the latest and now my trip will have to be cancelled thanks to PostNet. Inconvenience at its best, poor poor service!!