Is it possible to change the 'wifi password' on just the extender/booster? 
We purchased the extender because our housemate set up a new broadband while we were away but didn't think about the range in our property so we set up an extender which we only want access for myself and my partner to reach our part of the house and don't want our housemate to access it. 
(I know it sounds a bit petty but we have a lot of issues with our housemate! lol)