How to block someone from using my Wi-Fi network.

utkarsh_shukla Posts 1 Registration date Thursday April 14, 2016 Status Member Last seen April 14, 2016 - Apr 14, 2016 at 03:59 AM
First of all let me tell that I am having Binatone router. One device was connected to my Wifi yesterday and using my internet continuously. I have tried to change my Wi-Fi password but the device connected again in 20 seconds. I have also tried blocking MAC address of the device but no success, device is using my internet continuously. I am giving the details about device below. Waiting for answers.
MAC Address/OUI Vendor {Company}
B8:B4:2E Gionee Communication Equipment Co,Ltd.ShenZhen