Unwanted AirG subscription

I am another customer that has received these unsolicited SMS's saying \Your recurring R7.00 Subscription to AirG Social Service will be billed on ***X.)<br> <br> I never subscribed to this service and when I got last weeks SMS thought nothing of it but now got another a week later. PLEASE unsubscribe me from this as the vodafone url in the SMS does not work and I have no other idea of how to stop this.<br> <br> I would also love to know how it is possible for a company to do this? How can they debit off my account when I did not give permission for it?"