A mobile station user is informed in real time of reaching of a threshold of data usage via a wireless communication network. An account of the user has a maximum data plan limit defined by the user's plan and a data usage balance reflecting an amount of data usage remaining under the plan. When data usage corresponding to the requested data session does not cross the threshold level, a slice of data for the data session is allocated. When required data usage corresponding to the requested data session would cross the threshold level, a reduced slice of data is allocated. Data usage is counted in real time during the data session, and a notification of reaching the threshold level of data is sent to the mobile station in real time, at the time when data usage under the user's account reaches the threshold level.