There are surgical and liposuction methods for getting rid of a double chin. They are expensive, sometimes risky and do not always turn out as you expected.
There is another approach to this problem. You should realize that a double chin is the result of two factors. The accumulation of fatty tissue and a loss of muscle tone supporting skin under the chin.
By strengthening the muscles under the chin thru exercise, they will tighten up, pulling the skin and fatty tissue upwards back into place. It may not do quite as good a job as surgery, but for most of us it will be a great improvement.
Here is a Doctor approved exercise to help accomplish getting rid of that double chin. Doing them daily, you should start to see results in about 2 to 3 weeks
Sitting with your back straight in a chair close your mouth. Using either hand place the backs of your finger lightly touching the skin under your chin. With the tongue press hard against the roof of your mouth. Feel how the muscles and tissues under the chin were pressed downwards against your fingers. That is exactly what you want the exercise to do, but without using the tongue to help.
As you learn how to do this without using the tongue, let your fingers offer a resistance to the muscles pushing down. Keep in mind you want to do the exercise daily and in such a manner that you create a sense of fatigue. To fatigue the muscles consider doing the exercise more rapidly.