I need help with Vodacom

I recharged with 30 Rands worth of airtime and when I tried to buy data I got an error message then next my airtime is finished. I had to buy another 30 Rand airtime. I had stopped buying airtime and data for Vodacom for this reason. The last month I stopped buying from them they took my 50 Rand worth of airtime and in both occasions I had no airtime advance and no phone calls made. My friends have left Vodacom for this very reason to go to telkom and now I'm going to join them if my airtime is not returned. I feel helpless and vulnerable to have such a big company take from me as though the data and airtime aren't expensive enough. When I called their customer service I wasn't given an extension to talk to a consultant instead I had machine tell me that my airtime was taken by my apps and it's funny that since I'm using to dual sim phone I have mtn network as well and my airtime on MTN has never disappeared because of the so called apps. With MTN I see where my airtime is going while Vodacom continues to take my airtime just like that. I need help please.