Change passcode lost phone

You have to have the device to change the passcode. You can change your Apple ID password.

If you know the password.

 Apple ID Password Change.      

 What to do after you change your Apple ID or password - Apple Support     I suggest doing this before you change your Apple ID or password.

If you forgot the password.

For the Apple ID password, enter the Apple (iCloud) ID and click Forgot Password. See if you can get an email option if necessary.

Apple ID - Manage            

Apple ID – Forgot Password            

You can't remotely change the passcode. See the Apple Support article(s) below.

Passcode - If you forgot the passcode for your iPhone or your device is disabled.