Or use more then 1 isp. I don't know if they tell you how much of your time you've used up. Have maybe 2-3 or 4 of the free isp's that you use. Ok netzero is used for the rest of the month, now it's on to ..... A hassle, but it would give one more time to be on per month.
There is at least 1 there that is available for Canada only on the page I linked above. No idea what country you are in.