FIDO Cellular Over Charges

My Family was using Fido mobile service and I was shocked when I saw the bill of my daughter, I was the one who is paying her bills and I noticed that she was being overcharges which is ridiculous because I know she seldom use her phone and when I asked her about it she told me that she used the internet to communicate with her friends and rarely her phone. When I called their customer service and complained about it they can't offer any resolution. Class action suit should be taken against them, I worked hard to earn my money and they just rip me off.