If you do prepay for one year then have it dropped to a monthly basis before the year is up then they will go back and charge you monthly for all of those months. For example, you paid for a year of AT180 in which you get charged for only 11 months instead of 12 and 11 months go by and you decide to go monthly. You will get back NOTHING (because someone would have to not be thinking if they go this route). If 10 months go by you will get back 1 month, 9 months go by you get 2 months back, etc.