How can I upgrade my iPhone 7 to iOS 16?

An iPhone 6s, iPhone 6s Plus, iPhone 7, iPhone 7 Plus, or iPhone SE 1 isn't capable of 16 or above; they require an A11 or better CPU.

(259786)

Nope. the only way to do that is to trade it in or sell it and use the money to buy a new phone.

iPhone 7 did receive a security update yesterday, iOS 15.8.4 so it’ll continue to be safe for use.