MY AIRTIME KEEP ON MISSING

I don't know what else to do or who else to turn to regarding VODACOM and my missing airtime. Everyday I keep checking my airtime if its still there - that is so abnormal. Every time I will call Vodacom customer care screaming and screeching because my airtime is MISSING. Every time they will tell me that I subscribe to something which I always tell then in return I NEVER subscribe to anything, and they will promise me that they have cancelled the "subscriptions". I even went as far as resetting my phone back to factory default and deleted "everything" on my phone. But same thing keeps on happening. On the 10 February I loaded R200.00 airtime, I did make calls, but you cannot tell me that 3 days later I'm left with R19.00 worth of airtime. Somebody please help!!!!!!!!