PHONE STOLEN!

If your "friend" knows your Apple ID password, then they most likely, have full access to this phone. There are a few things you can try at this point:

• Immediately, change your Apple ID password.
• Use the Find My app on iCloud to attempt to lock this iPhone. It would become "available" once your "friend" attempts to connect it to either a cellular or wireless network with Internet access.
• Contact your cellular provider and inform them that this phone is stolen.
• Needless to say, but if your "friend" will not return your phone, you need to contact your local law enforcement agency to report it stolen as well.
• Finally, for future reference, NEVER share your iPhone's passcode or any of your passwords to ANYONE.

These would be the steps: https://support.apple.com/en-us/HT201472

But, if you gave someone your passcode, they can change your settings, etc.

I'd go to the police. Especially since you know who the thief is.