IPhone 4 MSG that settings have been changed (but not by me!)?!?

Twice I have awakened to a message on my iphone 4 that my settings have been changed. The first time this coincided with my Yahoo mail acct getting hacked, about 2wks ago. After that, I changed my Yahoo password and enabled Restrictions, but I got this MSG again today. Who or what is making changes, and how can I stop it? Thx!