Free minutes usage allocated incorrectly

I want everyone to know that has got a Vodacom contract with free minutes that you receive on your package that they are being very sly about the usage of it. I checked my voice minute balance yesterday, it said that I have got 600 min that will expire on 31.01.2020 and 318 min that will expire on 31.12.2019. So automatically I started phoning a few people yesterday to use up the 318 minutes before it expires today. Only to check this morning and my totals now say 600 min that will expire on 31.01.2020 and 318 min that will expire on 31.12.2019, that baffled me a bit because now the minutes that expires later is being used first. According to my knowledge your old minutes that you have already paid for that carries over to the next month must be used up first and then the new minutes in the new month that you also paid for must then be used and carried over if anything is left.

I phoned Vodacom Business call centre and they told me that unfortunately their system are set up like that for everyone and they can't change it. They said that they carry over the minutes to give you a chance to use them, but the new months allocated minutes gets used up first and then you get the use the carried over minutes from the previous month. They told me that I must phone Vodacom head office if I want to take it further, for they can't help me. I phoned the number they gave me and came out to the same department again, then I got a *** number that I phoned, they put me through to someone and the phone cut off eventually, I never got through to them. I have read their contracts that I have got and it refers you to the "free minutes and bundle expiration terms and conditions" on the vodacom website, I checked there and can't find anything stating that it is how to work with the minutes being used and allocated. Vodacom is being dishonest in how they work it and all I want out of this is that they need to set it right, we pay for those minutes and would like to use it.