the hub comes with default wpa2 so unless you have given someone your passowrd or they have got it off your hub it is highly unlikely that someone has hacked into your wifi. are you sure ity's not someone using btfon assuming you are opted in to BTFON?
As stated, it's unlikely that someone has accessed your hub. But you can change the wireless key and the hub admin password by entering 192.168.1.254 in your browser, choosing Settings, and looking for the details you want to change.
While you're there you can also alter the SSID (the name broadcast by the hub) to anything you like. I've seen this recommended as an additional security measure, the theory being that a potential hacker would find it easier to access a router if they knew the manufacturer and type. That's probably a bit far-fetched but I changed my SSID to something silly just for fun.