Charges for a call I didn't make

[Anonymous]

Hi All. After some advice. I have an O2 contract for my sons phone. Last week he told me that he was unable to make calls / get 3G, 4G. I called O2 and was told that there had been a block put on the phone because a four and a half hour call had been made from his phone (in the UK) to Cyprus. This call racket up a charge of c£250!!!
My son is 12 and knows NOBODY in Cyprus
As a family we know NOBODY in Cyprus
The call ended just before midnight on a school night
My Son isn't allowed to take his phone when he goes to bed
Quite simply - the call didn't happen from this phone.
The lovely people I spoke to at O2 (actually that's not sarcasm) said they would start an investigation and come back to me within a week as the process takes 5 days....report was logged on Monday this week.
I know (hope) I'm worrying about nothing here but I want to know that the investigation will be able to prove we didn't make this call. How does that happen and what's the process.
Thanks
Morgan

[Anonymous]

Brilliant....I'd apply but they want someone fluent in German.
It's just bizarre!

[MI5]

I have to agree - it is most strange !!