Your pac negates the need to give notice as the contract will end when it's used.
Give your new network your pac on the 14th June and it will be actioned on the 16th.
O2 will still have charged you for the next month (as you pay a month in advance) but they will refund you that cost 14 days later.
I have no affiliation whatsoever with O2 or any subsidiary companies. Comments posted are entirely of my own opinion. This is not Customer Service so we are unable to help with account specific issues.
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