MTN poor service.

I have a pay as you go card which is fitted in my alarm system to send me an sms if my alarm is triggered, I put R 180 onto it, which should last forever, however in June the airtime was gone so i put another R 180 onto it which lasted a week. On checking i found that, somehow, there were 8 subscription on this card. I deleted all and put R 60 on the card, this lasted 3 weeks and again, on checking there were 4 subscriptions loaded. i deleted them and phoned MTN call centre who told me this was all my fault as I was loading them, I then spoke with a supervisor who also told me it was my fault and I would not be refunded. this card sits in my alarm, in a cupboard and the only contact it has is with MTN. However when i received my invoice for one of my other cards, my data card, this had an extra R 150 usage on it and on checking, this card had 4 subscriptions loaded, again on phoning in I was told it was all my fault and there would be no refund. I then checked my wifes phone and also 4 subscription were loaded, i didn't bother phoning as I am sure I will get told it was our own fault. These subscriptions are being loaded, and charged, with no authorisation being given and without being requested. I am now down by about R 700 and MTN will take no responsibility at all and do even offer to check how these subscriptions are getting loaded. i find this extremely poor service that is also verging on *****.