Why do you feel cheated? Apple updates their line up every year in September and older models recieve a price reduction. That has been the case since September 2012. You need to inform yourself before you buy something that expensive.
If you bought your phone in an Apple Store or with Apple Online, you would have a 14-day return period where you would recieve a full refund. But since you have your Xr for a month already, that time frame is over.
You can also make use of trade-in and trade in your Xr for the 11. But you'll need to wait until September 20th when the pre-order process is over and you can buy those phones in the store.