Being charged R3 a day for a service I never subscribed to.

I have been receiving SMS's from MTN saying that I'm subscribed to "MTN Play airG *R3/Day". Initially I thought this was a **** SMS because I never subscribed to such a service so I ignored it for a while. I later realized that it was actually costing me nearly R90 of airtime a month which is the majority of airtime I get in my package.

The SMS provides a link to 'unsubscribe' which takes me to a website that asks for a username and password that I don't have because I NEVER subscribed in the first place. I started receiving these SMS's in March and have been losing money to it since. Please unsubscribe me and refund my airtime!