DATA and Content Charges wrongfully on my account

I phoned customer care this morning to report data being used on my 3G account while the sim card and modem is locked away at home and I am at work. This modem is not even plugged into a computer, data goes off at every which hour of the day/night, while I am at work. Customer care told me to phone 1555, 1555 told me to phone 808 and so we go back and forth, nobody knowing who I should speak to. Eventually back to 808 I told my story and got put on hold for 22 minutes and then the call dropped.Previously I reported content charges on my account, the response I got was unsatisfactory, I reported the consultant to customer complaints, nothing happened, MTN still took my money via debit order. I again send an email to MTN stating that I want to cancel my contract due due to unsatisfactory service from MTN regarding queries and charges billed to my account without my knowledge, I got a two month free sub offer, nothing sorted out. Of my 5G data, I have 300MB left for the month and I DID NOT USE IT. Please MTN tell me where my data goes?