airtime

hi I am always experiencing a problem with vodacom concerning airtime. they have this thing of taking cents from the airtime i have on the phone, just this morning I took an airtime advance of R5 wanting to buy minutes of R5, immediately after I finish buying the airtime one cent was gone, what can I do with the remaining R4.99 obviously am forced to buy another airtime. just imagine if they take one cent from each of their customers how much they are gaining per day? this thing has been going on for a while now it has to stop, i heard many people complaining about this. sometimes you know last night you had so much airtime balance on your phone the next morning one cent or two cent is gone. what kind of games are they playing? and some people don't notice this thing is happening on their as maybe they have lots of airtime. nowonder many people are joining other networks.