unnecessary billings

I'm really struggling with MTN, I had laid a complaint on Hello Peter before regarding my airtime been taken everyday by MTN, however I have no subscription. I use my Midnight data and exactly at 05:45 in the morning I switch it off, check my airtime and find that it hasn't changed. after 6 when I check it again its all gone. MTN called me before when I laid my first complaint and told me they are aware of this and re imbursed me my airtime. they said they would call me back but I'm waiting while this keeps happening. I want to prot my sim but now they are telling me to wait till month end since I'm under onetoone data contract. in the mean time what do I do.