How does the network not allow you to use your own airtime that you've purchased!!

<p>I moved to Cell C as I heard they're a cheaper network, it seems the only benefit of the network is their Whatsapp bundle, but can somebody please explain to me how Cell C can claim your airtime once you've recharged? If I purchase R10 then I'm only allowed to use R3 and the rest is like it's frozen and it disappears eventually, if I purchase data and it runs out then my airtime disappears, if I make use of their emergency airtime then it doesn't allow me to use the airtime however it takes my airtime + R1 when I owe the emergency airtime. This is so frustrating, seriously!! Def changing back to previous network. If somebody could give me an explanation as to why this happens then perhaps I'd understand but the consultant at the Cell C store just told me "I hear you but that's just how thr network is" .. Unacceptable! </p>