Investments in oil and gas companies, although they may track changes in gas prices, are not a perfect hedge by any measure. Also, such investments are exposed to risks that do not relate to gas prices, such as interest rate risk, operational risks and market risk. If you are seriously worried about your natural gas bill increasing, a fixed rate contract is the way to go. It's not a bad product/service.
That being said, I have found the tactics of the gas marketing companies less than savoury. Automatic renewals are a ridiculous policy. Incidentally, I worked for a gas and electricity marketing company in Ontario briefly in 2004. I was given a ridiculous and misleading sales pitch that I was supposed to recite for each potential customer. The drones that go around signing people up only get $75 per contract (maybe a bit more these days) and no fixed salary. So, have a little sympathy when they knock on your door (but keep your guard up).