Unacceptable exorbitant charges!

Absolutely ridiculous that we sign for a set contract for a number of months and an agreed amount and all of a sudden you decide you want to increase the premium even though the device is depreciating. You automatically add data without even asking if we want that added service. I did not sign for additional data. Further to this you charge me for it but it forfeit every month end when not used? I called twice and even spoke to a manger who told me this was because of the vat increase! Vat increase was canceled and hence this should have also! When I asked him this he did not know what to tell me and says he will call me back. Guess what? He never did! I called back spoke to an agent said she will investigate and yet again no callback. I am paying over 800 for 2 devices that have depreciated in value and are not worth a single cent at this stage and no they're not even iphones! How can you just bill what u want?