Return it and exchange for another craft, if it's not too late. Otherwise you'll need to ship it back after trying this below.
Look at the HD page and make sure the Wifi interference isn't off the chart for the area you are flying. Have you tried flying in different areas? Are you flying next to other Phantom pilots? If so you need a good separation from other controllers to minimize interference.
Set your video channel to a custom channel #20, then reduce your "transmission quality" to 4mbps. This should maximize your range, assuming channel 20 is not super busy with wifi traffic. Also, you can try using Windsurfer on your antennas to enhance range. If you install the 32ch hack in your smart device, fly on channel 30, 31 or 32, those are never busy.
Make sure to keep your antennas parallel to the legs of the craft. With windsurfer, make sure to always point the dish at the craft. The radar screen show you where the craft is if you happen to be beyond VLOS.