MTN airG charging me R3/Day for a service I never subscribed to.

I have just received an sms notification that I am subscribed to MTN Play airG! The message reads as follows: Reminder: Ur subscribed to MTN Play airG * R3/Day. For help call + ********** 7985. To unsubscribe click here http://m.airg.ca/out. The link leads to a website that requires a username and password that I do not have because I never subscribed myself. I did not subscribe to this service! I dialed *141*5# which states I am not subscribed to any such service. I also tried several other ussd codes to unsubscribe and all of them told me I am not subscribed to anything. I do not want to be subscribed to this and have no idea how to unsubscribe!