MTN prepaid airtime disappearing and recurring data bundles

I am unhappy with MTN airtime disappearing due to the purchase of so called recurring data which I didn't subscribe for. I bought a R200 airtime voucher. I use a router for data and switch off my mobile data. Even so, A 1GB data bundle was magically bought. Funny enough I didn't receive an sms notification from MTN as one usually does when they load airtime or buy data. I am irritated that even the answers provided allude to it being the customers fault. Annoyed customer!