Well, I saw the link to the pro-rated first bill. They charged me for 4 days and a full month in advance. Does this mean the last month I use before I cancel, I don't have to pay last months bill?
As this thread so far has been clear as mud, your final bill should contain no charges for your plan, as you would have paid for that month's service on the previous bill. You would see charges for any overages incurred during your final billing period though, along with any tab balance still owing.