Whenever I want to study, I think about stopping playing with my mobile phone after 10 minutes of playing, but I always procrastinate, and then I play with my mobile phone until I go to sleep, without the energy to complete the task of the day, and then postpone it until the next day... 
How old are you and in which class do you study ?
The best way is to give your mobile phone to your parents for the time in which you study and make a commitment with yourself that you won't use the phone unless you have completed your assignment/study.