Data Contract Issues

I got into a data contract with Vodacom last year in August, everything was ok until May this year when the 5Gigs loaded data (in a router) does not even last a week, and I only use this data in the evening when I get home from work, as I use the company's Wifi during the day. I reported this around July but I still haven't gotten any feedback. I feel like i am being **********, and i really just wish that I could cancel this contract and go to another service provider. I end up spending a lot of money on data a month as I constantly need to recharge. This is really driving me crazy now.