Replacement of device in 7 days

Hi,<br> <br> I took out a contract for an iPhone 6s on Wednesday the 27th of Jan 2016 and was advised that if the device was faulty it will be replaced in 7 days. The device is heating up after 5 minutes of usage and the voice quality is poor. The contract was issued at 13h33 on the 27th of Jan and I went to the store on Wednesday the 3rd of Feb at 10h30 only to be told that the device can be sent in for repairs, who is this possible as it should be replaced.<br> I was told that this was the 8th day, unless you changed the metric system I fail to understand how this is possible.<br> <br> Can you issue me with a new device and you can do what you want with the device that was 7 days old on the 3rd of Feb.<br>