How to upgrade iPhone 11 to 12

Use this like to buy buy an iPhone 12: https://www.apple.com/ae/shop/buy-iphone/iphone-12

1. choose your storage and color
2. Select Yes for: "do you have an iPhone to trade in?"
3. Fill out information about your iPhone 11

You have to choices:

1. Trade-in through Apple, as per this support article:--> https://www.apple.com/shop/trade-in
2. Sell your current model 11 on your own, then add the money to buy a newer model.

Regards

Giulio