Hellllllpppppppp me i've been hacked

[Addlay]

recently my phone was hacked after I downloaded the app from the market Google Play I started to notice that my phone was acting really crazy because the makers of the app 4shared had used a Vocal terminal emulator to program my phone where they had total access to my phone files when I found out and begin to try to remove these mounts the beginning to manipulate my phone how can I do a master reset to get them out of my files I have a galaxy attain 820