My iPhone will not restore to factory settings
I've purchased a new iPhone. I wish to restore my previous phone to factory settings. If I do the method via the iPhone. I'm prompted to upload Data to iCloud, my new phone is fully up to date so I select Skip Backup as I do not require this - the process just hangs indefinitely.
I try the method via iTunes, and it tells me it is downloading software (why?), but again just hangs indefinitely.
I need to restore my old phone to factory settings in order to return it as part exchange.
Could someone please let me know how to do this?
Thank you
iPhone XR