Randomly subscribe me to an SMS package.

I purchased sms's with my points like I do all the time. Yet today I randomly received an SMS from you saying:

"Y'ello! You subscribed to SMS50. Your anniversary date will be ********** 1."

I did not subscribe to anything or do anything different than I usually do when I purchase smses, and I do not accept being billed for this. Please remove this from my name and confirm that it is off. I did not at any point give any permission to subscribe me to anything.