How to get rid of repeating OS update notifications?

I have STL100-1 and keep getting the 10.3.1 update notifications. I'd expect to get just a single notification which I can get rid of just by marking it as read. But no, the notification comes back every day. Is there a way to prevent this? (I don't want to update).

I'm on Bell and I get the same thing everyday, really annoying...would love to know how to stop this. The out of the box 10.3.1 works flawlessly on my Classic and I see no reason to update.