this exact thing happened to me last year. they had been undercharging me for about the same time period. come december, after a meter reading, they decided to charge me for the full amount at decembers rate. decembers rate just happened to be the highest rate of the year. i called their customer service and complained on how they charged me. i know i used the utility, but the way they went about it was sketchy at best. after a few weeks of going back and forth on the phone, they finally agreed with me that the billing at the december rate was wrong, and i demanded they charge me at the lowest rate over that time period, simply because they couldn't prove when i used the utility.
long story short, check your bill and see what rate they charged you for the undercharged utility you used. if you're on a flat rate, you may just have to pay it. if you're on their variable rate, ask for the whole thing to be charged at the lowest rate over the time period in question.
edit: they told me that they are required to come to do their own reading twice a year. even after my situation, they still come less often than that.
aside from the few 'buttwipes' who feel cool to berate people, there is some useful info in this thread. luckily, you're a female, so you'll get all their help. it's not often some of these guys actually have contact with the opposite sex. so when they do, they'll do whatever they can.
http://forum.calgarypuck.com/showthr...+golden+flames