A Week wait for a new Device

On Sunday 7th November I took my iPhone 6 in to the iStore as the device was faulty. It was then sent to the service department which only reached them on the Tuesday, which I am told is also in Durban. Upon assessing my device I was told a replacement device would have to be ordered. I am now going on a week with no phone and my phone is my business. I do not understand why the iStore cannot just replace the device with a new one at the store rather than having to wait for stock to come to the service centre then be sent back to the iStore. I have always purchased Apple Products but the service in this country sucks, they are very happy to take your money and make you pay for extended warranties etc but when it comes to having to give you a replacement device there is always a big story, the delay in waiting for a new device is rather infuriating. In America any faulty device is replaced in the store on the same day yet we have to wait over a week for a device to arrive. I also kept getting told by the staff that I will be called when they have an update for me, but how am I suppose to answer a phone that I do not even have????