Pay by the Day Plan

I understand that if I purchase the Pay by the Day plan, e.g. $2.00 a day, if I have not paid for a given day, even though I may have $10 in the "kitty," I will not receive a call on any day on which I have not paid the $2.00.

Is this correct?

If it is, it does not make sense. I would have to pay the $2.00 every day to ensure I do not miss an incoming call.