basicaly.

if you were to buy now 18/11/12 it would run for 1 month and end on 18/12/12 it would cost $20. if you then took a break and diddnt renew, you would have to pay $20 again. $15 is only for renewing because you take a break there is a gap in service which means it isnt a renew.

also yes you can cancel before the month ends if you only wanted 1 month.

hope this anwsers your questions.

GV