on 24-08-2023 18:57
on 24-08-2023 19:00
Upgrades cancel and replace the current contract.
on 24-08-2023 19:46
If your contract is from O2, it will be a Refresh contract ( Guide: How does O2 Refresh work? ) - you *may* be able to #"flex" up to a Plus Plan - but it will cost more and may not be offered to you in MyO2 as a Flex option, @Fluffy50 - https://www.o2.co.uk/refresh/flexible-tariffs
Otherwise, as @MI5 says above, upgrade is your only remaining route to a Plus Plan.