Free minutes On cell phone-contract

On August 25 2014 I upgraded my contract with vodacom to a Smart M package. According to the contract I should recieve 300 Mb data.300 sms's ,120 free minutes per montt valid for 60 days. I soon find that the minutes are only for 30 days because when I carry over minutes I first have to uise the 120 minutes allocated during the current month.I made numerous enquieriesand although am told the minutes are valid for 60 days Ikeep on loosing minutes. Finally I lodged acomplaint and got feedback on 24/02/2015. I was told that although the minutes are reflected on my account as being valid 60 days I first have to use the 120 minutes before i start using the minutes carried because this how the billing system operates. I loose minutes and in fact the free minutes each month are only valid for 30 days. Mb's and Sms's are no problem. Please Help.