So sorry about this! The department will be back open tomorrow from 8am! Apologies for the delay to get this sorted.
An ESIM is an electronic or virtual sim, so instead of having a physical sim in the device they are able to operate without one. Not all devices are compatible with this service, so if you are currently using a physical SIM in your iphone SE handset, it is likely you will still need a physical sim. This will not be a problem, if you do require a replacement SIM as part of the package change we will send one to you - the other will keep working until any replacement is activated.
Virgin Mobile is not currently using the O2 network, we are currently operating throughout the Vodafone network. However, this may change at some point in the future.
I hope this helps! Do let us know how you get on when you call us back, we can offer further support if needed!
All the best.
Molly