Vodacom are you *****ing our minutes?

I queried carry over minutes from a Smart M contract. i noticed over a number of months that my minutes which were not used during the course of the month did not carry over into the new month. I was told that the LIFO principle is now being used i.e. you need to deplete your current contract minutes and then your carry over minutes from previous month will be used. If you do not use your contract minutes you lose the carried over minutes. Strange previously you used your carry over minutes first and then the new contract minutes, which meant you were depleting carry over minute first and then your contract. If you did not use your whole contract the unused minutes were carried over etc etc.. Now you just lose the minutes. I find this extremely unfair