How do you find your minutes used on line in your account. It doesn't make sense. On my account it says 0/173 airtime? Yet the page full of details of those minutes say 99 mins total. Why does it say 173??? And how much of the minutes are before 500 which is what I am supposed to be charged for;;;This does not make sense. How do I know what I have used in my plan so that I know its not going over?