How to update my phone ip7

See Update your iPhone, iPad, or iPod touch

https://support.apple.com/en-us/HT204204  and the related compatibility guide below.

iOS 13 and iPadOS are compatible with these devices - Apple Support. Your phone fits in here. 

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If you have a problem updating,

See If your iPhone, iPad or iPod touch won’t update

https://support.apple.com/en-gb/HT201435

Also, see If you see an error when you update or restore your iPhone, iPad, or iPod https://support.apple.com/en-us/HT201210  and

iOS update and restore errors https://support.apple.com/en-us/HT204770

Get help with over-the-air iOS updates          

Have you tried using iTunes on a computer or Finder if running Catalina to do the update?

 Update software on iOS devices in iTunes on Mac