Disappearing airtime and lies from MTN employees

I bought airtime and data last week, and never used them as the phone I use for my MTN number died. This week I wanted to make a call and knowing that I have airtime in that SIM card, I put it in my working phone and tried to make a call but learnt that my airtime is exhausted. It did not make sense to me but I checked if there were any running appplications and there were none so I bought airtime again and made a call. I was left with about R36 and I took the SIM out of my work phone. A day later I needed to make a call again so I tried to use the R36 airtime in my MTN SIM and to my surprise the balance was R0.00. I called MTN on 173 and spoke to Musa who then advised that I probably have running apps on my phone. I told him that that was the first thing I checked as it was not the first time. He said he is looking at the system as we are talking and he sees that there are some apps running and using up my airtime. I told him that that does not make sense because as we speak my airtime balance is 0.00 so any apps that were supposedly running should have stopped by now. He then put me on hold and never came back to the phone. My friends are also complaining about the same issue.