Hey N14SUT,
Welcome to the community and thanks for taking the time to post here on the forums.
I’m sorry to hear of the issues that you’re having with your voicemail pin, you would always need to use the voicemail pin, when accessing voicemails outside the UK.
I would be happy to take a further look into this for you but first I would need to confirm a few details via private message, please look out for my message and we can get started.
Kind Regards,
Steven_L