Exchange

did you order it from Apple?

Once you receive it, my understanding is that you have 2 weeks to return it. So if you were within this window, you could return it and buy a new one, but I don't think you'll find a way to exchange it

You have exactly 14 days from the date you received the phone to exchange it. If you have had it now 3 weeks, you have missed the return window.

You can certainly ask Apple, but they usually don't make exceptions to their return policy.

I'm not being rude when I say this, but unless you never read news on the internet, it's been widely reported for many weeks and months when Apple would be releasing the next generation iPhones. It's EVERY fall and almost always in September.

We are all users here on this user to user forum. You'll have to go to the store where you bought the phone and see if they will accommodate you. But as I mentioned, Apple is usually inflexible about the timeframe to return a phone.

Tomorrow is actually the official launch day for iPhone 13. Your Apple Store will be a madhouse tomorrow at the very least. People will be in lines outside the store who have pre-ordered an iPhone 13 model.

You're welcome and good luck with however this turns out. Worst case, you've got a new iPhone 12, which is a mighty good phone as it is.

That's truly fantastic!! Apple UK, may have some return differences than we have in Apple US. Still, it's great they accommodated you. Enjoy the new phone!