on 26-11-2020 18:25
on 26-11-2020 18:29
It will only reduce if you are on refresh, ie took your contract directly from O2.
If you bought from elsewhere, you can upgrade to a sim only tariff and just keep your current phone.
https://www.o2.co.uk/shop/sim-cards/sim-only-deals#deviceType=phone&contractLength=Featured