When it rejected my stupid security questions which were right I had to call them to reset them. Then I was forced to change my remembered password to one I can't remember. Apple is going overboard with security. I use almost the same passwords since I was first online with dial up back in 1996 and I never had my account hacked or comprised.
How were you notified of this change? Was it via an email? If it was you are being scammed. I get these phishing emails in my Apple mail every few days. They all tell me I need to change my password, my account has been frozen or will be deactivated if I don't take immediate action. If you can still access iTunes, your iCloud, email, etc then you're being scammed. Don't fall for it. I haven't been forced by Apple to change my password ever.