I received a junk mail letter from Sky, encouraging me to sign up. That was odd, since I'd signed up to the Mailing Preference Service. Not wanting to complain to the MPS straight away I rang Sky up to give them a chance to remove me from the mailing list. Unfortunately they weren't helpful, and said they couldn't remove me from the mailing list over the phone. So now I've followed the MPS complaints procedure and sent the MPS the offending letter.