Can I collect my new iPhone before trading in my Old One?

I have pre ordered new iPhone 16 through Barclays 0% and have selected in-store trade in and this has been applied to my Barclays loan. However is it possible to collect my new phone in-store and then post away the old phone that I’m trading in within 14 days? I don’t want to hand over the old phone straight away

[Re-Titled by Moderator]