Unsatisfied with help

We took a 3G rooted during the year and have been billed wrong twice now and I honestly use the rooted once a month for between 30 min and an hour and I get told that the data is finished. I really don't understand how one person can use 3G is that time period. When we phone in we don't get the correct answers to our question and we constantly been put on hold for hours. The most unsatisfying service that I have ever received and to yo top it all off its a huge amount to cancel the contract as this is their mess up and we still have to pay them it's utter bs in my book!!!! Waiting to see how long it will take them to get back to me or my husband.