Voicemail setup not working

[Ellie6]

I have recently transferred from O2 to Three. I have successfully ported my phone number. I have followed the steps to setup voicemail and it recognises that a PIN has been set. When I go into the Phone app (iPhone)  there is a red circle next to Voicemail that suggests that something is outstanding. When a voicemail is left, this is not available to me. My voicemail tells me that there are no messages although the caller left one.

[JonathanB]

Hi @Ellie6,

Sorry to hear about this. This could be related to LIve Voicemail as mentioned by @Clever-Trevor. You can read more about the feature here Introducing Live Voicemail.

If you've checked both the Voicemail menu in your iPhone, and also dialled 123 and can't find a message in either space, then let us know if Trevor's suggestion below helps?

[Clever-Trevor]

Three & voicemail is a mess. 
it’s a hybrid of visual voicemail on device ( with network coverage ) and old style dial in voicemail ( when no coverage )

unlike 02 & EE etc…. The 2 vm solutions do not sync.

so, it’s likely you have a red dot as either a voicemail unread on device or voicemail unread via dialup.
if you turn off live voicemail then reboot & turn on phone then turn live voicemail back on - this can solve it ( worked for me )

al the best.