Are We Going to Get in Trouble?

One day in the last week I got back home in the evening as usual after work and I found at home this strange letter from the gas company.. it was starting something like that: "To the Unknown User"... well it started good I thought... after reading through I discovered that we have being using the gas without paying since September and that was confirmed by my flatmate Billy who called the gas company to know about the letter...
Well we are not in charge of taking care of the gas because we're paying a rent which includes every kind of home expense (electricity, gas, internet, and whatever.....) We then called our landlord to inform him about this letter and he said ".. well you do not have to worry about that... just leave the letter at home that someone will collect it..." ... It was morning and I was a little bit sleepy than I said ok... but after that I thought.... hey wait.. are we going to be cut the gas out?... So far so good... but if some day we'll run out of gas we know now why......
The strange thing is that the gas bill is not being payed since September and I am wondering how it is possible that the gas company noticed the activity only now after three or four months we're there... and more... if the previous owner shut down the contract why we're still able to use the gas...? .... well stay tuned!