Prepaid is non-refundable.
Prepaid has no bills. You will never be able get a bill listing.
You pay in advance for the service you're expecting to use. It's your duty
to make sure you get the appropriate fill amounts for what you need.
With the postpaid plans, it's clearly written in the Terms and Conditions
that you're responsible for a full month, even if you cancel ONE day into
it.