Biggest Cheats

I have a vodacom contract and I receive R200 airtime on this contract at the end of every month. This month I received R200 airtime but I didnt even put the sim in my phone since the beginning of the month. I checkek my balance and it on R75. Its not the first time this had happened and the last time I was advised that it "backround apps" on my phone that taking my data and airtime. SO how do you explains this, cause I went to your branch ( I feel sorry for those guys) and they couldn't explain what going on. if my airtime is not restored I will take this case to ICASA and it would be interesting to see how you explain yourself's out of this