Info about split charge between ongoing rate and new 24M contract

[V1R61N202noAsk]

How does O2 split the interim payment when changing mid-month from ongoing rate to 24M contract

Details:
My previous ongoing rate (Virgin then forced to O2 but no contract) was £20.42pm 50GB Unlimited X 2
My new 24M O2 contract is £12.99pm from 13-Nov-2023 30GB Unlimited X 2
My latest bill 5Nov-4Dec2023 still charges £20.42 (I only use 1-2 GB)
Please explain?

Copied billing text: "My tariffs - O2 Sim Only Unlimited mins 30D 50GB : 05 Nov 23 - 04 Dec 23  £20.42"

[jonsie]

It will be a pro rata payment split between the old rate and the new tariff

[pgn · Accepted solution]

Refund of money paid less call or other charges on old contract, plus new tariff added from monthly pay date of previous contract, one month in advance.

It will usually be more than you are used to, bu just for one month. A shop would help you work this out. Good luck, @V1R61N202noAsk.

[V1R61N202noAsk]

Thanks
A pro-rata is what I would expect
but I cannot find any info / mention of interim payment between 2 monthly rates anywhere in the O2 T&C
and it looks like they are about to continue the old Virgin monthly charge which could not be changed for a long time (July 2023) as they were no deals available for new O2 transferred customers.

Correction: (found this)
https://www.o2.co.uk/termsandconditions/mobile/our-latest-pay-monthly-mobile-agreement
"5.10 Unless we say otherwise, Charges which are normally monthly but are being measured for periods of less than a month will be calculated on a pro rata basis"

[V1R61N202noAsk]

Correct but, at first, I did not understand "Refund of money paid @ old tariff" but that's because O2 charges 1 month in advance even if most-of-it should be already @ new tariff.
So
(Pro-rata here means number-of-days in new tariff --in my case 21.27 days+6.5 hours-- divided by exact number-of-days in this particular monthly payment so could be 28, 29, 30 or 31) 

a) Refund of Pro-rata advanced payment: - Old tariff / 29 x 21.48
b) Charge of Pro-rata new monthly rate:  + New tariff  / 29 x 21.48
c) Advance charge for the following month:  + Monthly new tariff
All tariffs being shown BEFORE VAT which makes calculations really difficult
That is NOT what I call CLARITY in O2 Billing !!!

[Oxonian]

@V1R61N202noAsk 

I do not think you are the first customer to be bemused by an O2 bill and I am sure that you will not be the last.