Mobile data usage dissapearing

For the last 2 months my data bundle of 1GB runs out with in a weeks time. Never happened before. I have to buy 3 GB extra per month. Vodacom says I must phone Autopage, Autopage says I must phone Vodacom. They say it will be wise just to turn off my data. Then I will not know when I receive any massages. I don't even use 3GB for office use. How is it possible for my phone...I don't use google on my phone, only Facebook now and then. I have a tablet for the use of google, Facebook and other applications. Nobody can assist me, or provide information for this sudden expensive change in my data usage. Please help!!!