You can hide and unhide channels from the settings of your Netgem device.
This can be done by navigating to Settings -> personalisation > Parental settings -> Enter your PIN -> TV Channels locked or hidden.
Locked channels will be available in your EPG but hidden channels would not be available. If you select a locked channels, it would require you to enter the parental PIN. To watch a hidden channel, you would need to know the channel number and press it on the remote control, this will require a PIN. There is no restriction as to the number of channels you can hide or lock.