Airtime

I am a prepaid customer but I have wifi so everytime I load airtime it is not alot of rand value but my issue is , and I have called and complained about this more than once. Each time there is a reason why whenever I load airtime by the next day it is gone. Sometimes I don't even make a call I have just sent a message or I have missed called my sister. It's shocking first it's data that was lost after a month now you just loose your airtime because (and this is the latest reason) if your wifi flicks off your phone just uses your airtime even if your mobile data is switched off...Sorry I can't accept all these excuses people that have prepaid accounts and only load small amounts of anything is because it's all they can afford. I have lost hundreds of rand on lost data and now airtime that just dissapears for games I never load or aps I don't know anything about and each time I phone I'm told it's sorted out and I won't loose my airtime anymore and it continues to happen it's really really annoying