2 Gig in 3 Days Impossible

On the 27th of July at 16:27 I bought a 1 Gig bundle on the first of August I should get another Gig with my contract, on August 2 they say I ran out of data, which is impossible, as I have broadband at my office and where not at home or downloaded anything at my house. When I phoned and ask them about it the lady said it shows that I was on, yes the modem stick was on a wireless rooster which is protected with a password and to far away from any other houses for someone to hack it. When ask to speak to her supervisor she said that she all ready spoke to him and that is that. I ask again I want to speak to him she said his on the phone, I Said I will hold on seeing that I have already been on the phone for 25 minutes more time would not matter. Who can I contact to explain to me exactly where and how it is possible for data to just vanish, now 300megs just vanish again after I bought another gig yesterday.