@CarlossparkyIf this is a new handset and new contract you will be good to go.
If its an upgrade then you will need to do a simswap, and full instructions are on the simcard wallet, the simswap can take up to 24hrs to complete, but is usually minutes.
Current Phone: Sony XPeria Pro-I and Motorola Razr 5G
I also have a Planet Computers Gemini
I work in IT as an Enterprise Messaging and Collaboration Tools Administrator (Office 365, Slack and much much more) and manage hardware both Mobile and Desktop / laptop, my desk is a bit like PC World
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We are all customers and dont have access to any o2 accounts