Looks like you should contact the sales team as they can help with that – message them on Social Media if that works best for you -on Facebook (https://o2uk.co/O2CFB) , Twitter ( https://o2uk.co/O2CTW) or Instagram (https://o2uk.co/O2CIG)
Or you can call them on 0800 081 0255
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Did you upgrade?
Your new contract would have been updated on your old sim so if you sim swapped, all you have done is transferred your new contract to a new sim.
Just use the new sim and it'll be fine.