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I've seen threads elsewhere from Vodafone UK customers saying they've got the Samsung One Ui / pie update so I'm assuming it's being sent out in waves and is dependant on phone serial and build number.
I have the update on my Note 9 but it's an unbranded Samsung phone.
Current Phone > Samsung Note 9 _512Gb > Model: SM-N960 Hybrid-Duos.
Samsung One Ui / Pie.
Samsung Gear s3 Frontier Watch.