Airtime Disappeared

Yesterday (19/07/2015), I loaded a R180 worth of airtime and made 3 calls (with each not lasting more than 2 min maximum). When I checked my airtime, I had R0.00 balance. How is that possible? I then called the call centre and was informed by Thato that I probably was downloading/was on the internet, of which I was not. I then loaded another R60 airtime, switched all my apps off and made ONE call. Guess what? I then had R0.00 balance. When I called the call centre again, I was informed by Daniel that only 59c was charged for that call and there is no other transaction on my account. Then where did the rest of my airtime go?<br> <br> I demand answers. How pathetic that now I have to reload airtime, in order for it to disappear???? No man MTN, after all this loyalty from me?