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Assuming your in the UK using the Nuc supplied by Vodafone UK and your using another networks sim card that is activated i.e connects to mobile data then if the Nuc isn't working you'll probably need the MCK Mastercode also known as an unfreeze code from customer service on 191 or Live Chat or the Vodafone Social Media Teams via Contact-us-for-account-specific-queries.
If you get stuck they can also provide the Nuc email address to contact them directly.
Unfortunately as they are not customer facing there is no contact number for this department.
Current Phone > Samsung Note 10+ 5G _256Gb > Model: SM-N976B.
Samsung One Ui 2.0 / Android 10.
Samsung Gear s3 Frontier Watch.