Mobile number suddenly showing as unrecognised when contacts try to leave me a voice message

[JP25]

From yesterday when one of my contacts calls me and tries to leave me a voice message they get a message saying that my number is not recognised.

The calls come through OK if I pick up - this is only happening when people are trying to leave me a message.

Have switched phone off & on; checked O2 network & my account - all in order.

Any suggestions as to what to try next please?

[MI5]

@JP25 

Check voicemail guide Guide: All you need to know about O2 Voicemail 901 

Or contact O2 Guide: How to find help & contact O2 

[JP25]

Thanks for suggestions - however the callers are not able to leave me a message as they hear "the number you've dialled (e.g. mine) is unrecognised".

All the callers are in my Contacts, so aren't Spam ones.

So for some unknown reason, since yesterday, no one can get as far as leaving me a voice message.

[pgn]

Try to dial ##002# to cancel all diverts, @JP25 

Or look in your MyO2:

If you are on e-sim, switching back to plastic SIM helped here:

https://community.o2.co.uk/t5/Tech-Support/eSIM-call-divert-issue-concern/m-p/1754317/highlight/true...

[MI5]

Have you tried turning voicemail off and back on again @JP25 ?

Also check your voicemail is diverting to 901 and not something else.

What happens when you call your voicemail?