Samsung B7722 wifi not working

Hello,

hi i have samsung b7722 duo..i used to use the wifi connection before.suddenly, i noticed that i can't connect to wifi anymore.everytime i connect with wifi, it says"disconnected" no response from AP". at first i thought the signal was just not good.but i tried to two other wifi connections in different place, even at home, and still, the same thing appears..please help me..what can i do?? thanks