Ref: http://www.fssr.ru/hz.php?name=News&file=article&sid=9409
This scheme uses prepaid SIM cards, which can send SMS messages to so called short numbers (http://en.wikipedia.org/wiki/Short_code) The person coducting fraud  rents these numbers so he collects fees from each incoming SMS.

Fraud scheme:
For each number, the prepaid number balance is periodically requested from the Carrier. As soon as billing system becomes temporally unavailable,the time window is used to launch a flood of SMS messages to "short numbers" so prepaid card balance becomes negative.

Status: to be verified