Unauthorized airtime deduction

For the passed couple of weeks, if not a months, R7 has been deduced from my airtime every night. I have contacted Vodacom 3 times. The first 2 times the call centre adviced me to cancel all subscriptions and the third time the lady was going to call me back after doing more investigation work into what is causing the problem, but never phoned back. Can someone please actually help me???