Are you rooted? If so, see my post (#7) in this thread:
Stop future OTA's
If not, the reminders should stop if you flat-out say "No, Thanks" to the update. Don't delay them, because it will eventually install! You can't stop the download, but you should be able to stop Big Red from installing it. The file will still be there, waiting for you to go back in and tell it to go ahead and install when you decide to.
If this doesn't work, then I don't have an answer for you. My apologies...