I cannot find an 0800 number on my bill

[Micky5050]

I called an 0800 number of the Times to cancel a subscription. Now they have charged me for next month and are asking for proof that I called them to cancel. 

However, my bill for May shows no call to this 0800 number. Where can I access this? My iPhone has only saved calls for June. None of the May calls are there. Why isnt O2 bill showing 0800 calls?

Can anyone please help?

thank you

[Bambino]

@Micky5050 I found the following link in a Google search. It's possible that the first answer may apply to O2 as well: https://forums.moneysavingexpert.com/discussion/5445074/0800-numbers-not-showing-on-bill