Sometimes retailers and Amazon resellers obtain phones that are known as grey imports @ASNUPhil
I assume Samsung UK can only apply the Care Package to a phone that has been released for usage in the UK. i.e a phone with a BTU CsC.
I assume you don't have Home Contents insurance to provide cover for your phone. This is my preference.
“ How and where to buy
Getting covered is easy. On Samsung.com, simply subscribe to Samsung Care+ at the same time as your buy your new Galaxy device (you cannot purchase it separately on Samsung.com). Alternatively, if you buy your new device from a Samsung Experience Store, you can buy Samsung Care+ within 30 days of purchase. Find out more detail about each option below. ”
Current Phone ~
Samsung Note 20 Ultra 5G SM-N9860_256Gb SnapDragon 865+
Samsung One Ui 3.1/ Android 11.