2GB of data finished in 3 days!!

every month i purchase the 1GB data bundle where u get another gig free. this lasts me the rest of the month. this month i bought the data on the 24th august 2015, by the 27th august the data was up!! how is this possible. the call center is useless, it takes forever to get through to a consultant to speak to then they have to transfer u to the data technical support. the call gets cut off or u cant get through to a consultant!! this is unacceptable the data is already so expensive now im getting cheated out of it too!! my data usage measured on my tablet is 400MB today on the 27th aug ....so its obvious that MTN is *****ING me!!!