Missing AIRTIME

My company phone have accumulated airtime to about R1600 so the company migrated to another package, so when i looked how much airtime is over it showed 16 minutes but 0 rand value, so how come? i even called the call centre that told me that the upgrade have been don e on the 17th of august and you have 30 days to use it! my air were there on 19 September and that was over 30 days and oh yes some of my other collegues still have their airtime and minutes just the airtime expire 16/02/2015 so why are the others faveroud!! this is unacceptable!