No airtime transfers for contract customers

Why should I buy airtime to be able to transfer to another number?! Didn't I already pay for the airtime on my monthly subscription? This is BS! They alwys call me on deals deals deals for yet another device and simcards in order to have available more data, but I already have with them THREE contracts! When one's data is finished, I want to be able to transfer airtime to the required simcard so I could load data on it by my own convenience! BUT when I call a consultant, I'm told that I must buy airtime to load/transfer airtime!!! So the R325 airtime that I have available on my monthly subscription isn't legitimate?!?! GET THIS STRAIGHT! I DON'T WANT MORE DEVICES AND SIMS TO HAVE DATA AT MY OWN REQUEST! I DON'T WANT TO PAY MORE THAN I ALREADY AM TO GET WHAT I NEED!!!!!!