How I can reset my iPhone

To reset your iphone:

make sure your iphone is backed up

To reset your iPhone, select Settings > General > Reset and click Erase All Content and Settings. Make sure you back up your iPhone first so you can restore your data later. In "Settings," scroll down and tap "General." At the bottom of the "General" page, tap "Reset."

To change password:

1. Tap Settings > [your name] > Password & Security.
2. Tap Change Password.
3. Enter your current password or device passcode, then enter a new password and confirm the new password. ... 
4. Tap Change or Change Password.

samara124 Said:

"How I can reset my iPhone: Why can’t I change my password"

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Password for what?

If you forgot your "Passcode", then hold it right there, and refer to this link: If you Forgot the Passcode on your iPhone, or your iPhone is Disabled - Apple Support. It would be the one you've always entered. If you do not know it, then look for it in a location you may have stored it in.

No Success?

Contact Apple support:

If you cannot get the above link to work, then contact Apple Support.

Apple Contact Info:

• Contact Us - Choose Locations
• Proceed from there, as necessary
• Why the Wait: Phone calls are taking a bit to go through at the moment, due to lots of calls. With the Coronavirus Pandemic, many are at home at the moment, with much time on their hands to contact Apple. So, just stay on the line, and you will get through.