My airtime is disappearing and I need to know why

On 13 and 14 August 2015 I loaded my phone with R60 airtime, again on 16 August with R100 and today with R30 and for all these times my airtime has just vanished. I contacted the Call Centre and the Agent, after explaining my dilemma, informed me that I have been surfing the Internet, which I haven't been doing. I made no calls, texts or used the Internet at these times, as my airtime disappear within minutes of it being loaded. After calling them again, I was told that of the R100 in question, they could only see a +- R34.77 disappearing and don't know what had happened to the difference. I am absolutely livid, as I feel that my query was not sorted and I am obviously not a ***gy-bank for feeding airtime into my phone without even benefitting from it.<br> I am at wits end and need this sorted ASAP. I have a reference for my call: ***. I want my money back as I have disabled all apps that could be running in the background. I have to say that the young man who helped me was courteous enough to try and sort it out. He was helpful but not as to pin pointing what was going on.