It doesn’t let me update my phone

What does not allow you to update your iPhone? See this for help. If you can't update or restore your iPhone or iPod touch - Apple Support

What do you see on your screen when you attempt to update your iPhone? Which error message do you see? Be specific when you describe what happens on your screen.

Furthermore, Make sure that your iPhone is setup to meet the following requirements before you attempt to update the iOS version-

• Your iPhone must have a fast Wi-Fi connection; you cannot update over cellular data or a cellular hotspot
• Ensure that you do not have a beta profile installed from a previous version
• The iPhone can not be in Low Power mode
• The battery state of charge must be above 50%
• Your iPhone must have at least 6GB or more free storage space
• Your iPhone cannot be connected through VPN
• You should leave the phone plugged in until it finishes updating, both to assure that it remains above 50% and to keep Wi-Fi enabled (Wi-Fi turns off when the phone sleeps if not connected to power).

Axel F.