They don't. they take the money your Customer Agreement says you need to pay them. That might include installation fees, extra data you or someone in your family purchased that month, a property tax recovery fee once per year, the cost of a service call, early termination or failure to return equipment fees.
Yes RARELY billing mistakes happen, that's true for any company that sells anything but, it takes only an email to email@example.com or a phone call to 855-463-9333 to get that corrected, if it was indeed an error.
I’m sorry to hear you feel this way. Are you currently experiencing any billing issues? If so, please allow us to review your account and see how we can assist. Please give us a call at 866.945.3258 or send us an email to firstname.lastname@example.org