Calls diverted to an unknown number

[Citron2010]

Hi,

I'm having to resort to posting on this forum as chat doesn't work and support lines aren't open.

I'm reporting this on behalf of my father who's 90 and not great with tech.

Whilst trying to change the amount of time before calls are diverted to voicemail, I noticed that his calls were being diverted to an unknown number if he's not reachable or if he's on another call.  I tried calling that number, but it just goes straight to voice mail.  I don't want to publish that number here, but could there be any explanation for this?  I doubt he's set that up himself either deliberately or by accident.  I've now reset both scenarios to divert to voicemail.  

Thanks

[Citron2010]

So I called my Dad on his landline and asked him to call 901 and put it on speakerphone - and - the first message played back was the one I recorded when dialling the mysterious number.

It's a pity there's no information on O2's website that explains this (at least none that I could find) - as it's pretty understandable that people might get more than a little spooked seeing that their phone calls were being diverted to an unknown number.

[MI5]

Thought so.

The one I posted was the call from abroad number but I couldn't find the UK long number @Citron2010 

[MI5]

'+447802 091901' or 07802091901 @Citron2010 ?

[pgn]

Does this Forum query from back in the day help, @Citron2010 -

https://community.o2.co.uk/t5/Other-Products-and-Services/Strange-call-forwarding-numbers-NOT-set-by...

Another one answered by our very own @MI5 ably accompanied by @jonsie  👍

[Citron2010]

Neither of those.  But the number must be unique to my father mustn't it?   I called it, got to a voicemail, left a message, and when my Dad called 901, he got that voicemail I'd just left.  If it was a shared number, how would it "know" that my voicemail was for my father and no one else.

[Citron2010]

It certainly sounds like a similar problem.  But as I've just replied to another poster, the number that was being diverted to must be unique to my father.  I left a voicemail on it and my dad picked it up by calling 901.

[MI5]

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@Citron2010 wrote:

Neither of those.  But the number must be unique to my father mustn't it?   I called it, got to a voicemail, left a message, and when my Dad called 901, he got that voicemail I'd just left.  If it was a shared number, how would it "know" that my voicemail was for my father and no one else.

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No, not at all, in the same way that 901 is not unique.

The only way it could be specific to your father is if it is actually his number.

[Citron2010]

When my dad calls 901 from his O2 number, the 901 service "knows" who he his by his phone number so plays back his voicemails and no one else's.

But I called that mysterious number (which isn't his) from my phone (not O2) and left a message.  My dad then called 901 and picked that message up.  How could the mysterious number or 901 "know" that the message I'd left was for him and no one else unless that mysterious number (which isn't found anywhere by Googling) is unique?

[MI5]

@Citron2010 

I've no idea as I'm not a network engineer and no one here will know how it works without guessing either.

Anyway, your original question is solved as per my first answer. If you wish to know more about how the network works and facilitates voicemail activation I suggest a new topic in the discussion section of the forum.