Never giving the write amount of data !!!

For the 3rd month and countless phone calls .. I have received in adequate data for the data bundle as per my contract ! I have disconnected cellular data from all apps and some exactly what Vodacom said I do in terms of turning off app refresh. Basically I can account for all my data usage but I have a severe short fall in the amount of data they give me per month and I am not the only person this is happening to ! Please assist or comment if anyone has advise