Removing Devices

In this case we would like to know more details to help you on this, since you have not mentioned your modem model number.

May i have the modem model number.

If this is a gateway combination of modem and router then you need to perform hard reset on the modem then you need to change your network name then connect your required devices to the new network name so the devices which are not needed on the connected device list will be removed.