how to sign out icloud and we dont know the password

Apple ID address and password is required to sign out , if you don't remember it reset the Apple ID password If you forgot your Apple ID password - Apple Support ( also password can be reset using the link https://iforgot.apple.com/appleid#!&section=appleid from a web browser ) .

Once done Sign out of iCloud on your iPhone, iPad, iPod touch, Apple TV, or Mac - Apple Support

In case if you want to use another Apple ID already created With its own account credentials . Sign in with your Apple ID - Apple Support

erene17 Said:

"how to sign out icloud and we dont know the password: i dont know what is a password of this icloud"

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Troubleshooting iCloud Log Out:

Two things here...

A. "No Service":

"No Service" is shown on the top-left corner of your screen? So, go here to fix that: If you See No Service or Searching on your iPhone or iPad - Apple Support

Screenshot:

B. Connect to WiFi, Instead:

Being that you are trying to use Cellular while getting the No Service error, use WiFi log out successfully.