DATA JUST GOING MISSING

I have 3 vodacom contracts, each month we get data, by the 3rd of the month the data is finished, we have to load new data on the phone's, my husbank loaded 2gig of data and the next day it was finished how is this possible????? When you phone the call centre to assist you the people just say check you settings on the phone - and very rude person that answered the phone think they need to get other jobs if they do not want to work in a call centre, we have disables all the applications etc that can use data and still it doesn't work. i know i am not the only person complaining about this, i want to know how i can cancel my contracts with vodacom before the end of contract cause it is costing me more to be on contract than pay as you go or vodacom should refund me all the data i had to buy the past 2 years. i am really disappointed in vodacom they where always the best cellphone provider but not anymore. i need to get solutions otherwise i will have to take this matter up.