Just so you know... you are charged the month after the service is used, not in advance. Ex.. Your still cycle begins on April 20th, and runs until May 19th. The charges relative to that bill cycle, would be due the following month, 3 days before your bill cycle close date. In this instance, your 4/20 -> 5/19 bill cycle, would be due 6/16 (one month after close, minus 3 days), provided there is no delay in the processing of your bill, in which case your due date would be your normal due date + the number of days it was delayed in processing. Just so you know. To me, it sounds like it was just a glitch in the system, and if they do find it, you wouldn't be billed for the time that it's happened. It's not your fault they are billing you incorrectly, so they wouldn't actually add-on charges for the time you should've paid for unlimited sms'ing, provided that you are indeed getting the service currently.... so just leave it as is, if it's working out for you. Not a bad deal, but I've never seen that happen before...