are you sure that your current SIM isn't one of the "push out to size” type that you can make to the size you want?
If it is, this would explain why Virgin haven't sent a new SIM with your new phone. Simply push the middle out making the SIM smaller to fit your new iPhone.
If this isn't the case. I'm afraid that you'll need to give the Virgin mobile team a call on 789 from a Virgin mobile or 0345 6000 789 from any other phone & request a new SIM of the correct size explaining that you didn't receive one with your new phone.
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