Preventing automated subscriptions in itunes

Hi

Last year i got caught out and paid for an annual subscription for a magazine that i really did not want, because i did not know that you had to turn off the appropriate button in 'general ...restrictions'. I still think this is a really poor mechanism that must catch a lot of people out. The anniversary for that subscription comes up in a few days and i shall remember to restrict that facility this time around. My question is this, i have other magazines that i do occaisionally purchase, manually, one by one, no annual sub, but i am fearful that in un-restricting the facility in order to purcahse the magazine that i am opening the gate again to the annual subsciption. How do you say 'no' once and for all?