Vodacom data monster

So after setting up my data that as soon as it runs out, it automatically purchases 100mb, this happens. My data runs out and I get a notification sms. Same time a notification comes up asking me to confirm my purchase of data (no other details). I confirm, believing this to be the 100mb I set up and the next thing I get an sms confirming my 10gb for 7days??!!! I never even chose to purchase that! So I log a call and weeks go by I get an sms saying the case was handled and closed. No explanation, nothing! So I call to follow up and it's explained to me that it's my fault because I confirmed....Not a sorry for the inconvenience sir, here's 100mb on the house, or we'll credit half the amount... nothing! Suck it and pay! What horrible service from the data monster.