you cannot "hack" a wifi signal from an ordinary wifi access point with a strong antenna, as described in this case.
the access points range stays the same no matter how strong an antenna you are using to apparently hack someone's wifi.
in other words, the strong antenna can reach the access point from a KM away, but the little access point cant reply back, its too weak.
anyway.
there are a couple of possibilities as to how your bandwidth could be used while your computer is off.
one is multiple concurrent logins allowed. the ISP should be check this immediately, but they don't, guess they a bit "aan die slap" a quick check on their aaa radius server should show this.
another is a fault on their system where duplicate accounts are created or IP's used or some such, where you and another subscriber are using the same bandwidth allocation. this happens few and far between but it still happens. ask for a new username and allocation from a different dynamic IP pool.
OR
your ISP could be correct and its windows update, by default windows updates at 3am, sometimes its even set to wake the PC to do updates, then the question is, can your connection download 7GB in 2hours or what ever it was, between 3am and 5am...
I highly doubt its updates, this just sounds like a lazy support answer.
