Hi @Luke1931 ,
is this is referring to an issue related to your voicemail I would recommend reaching your network provider to see if this has been set up correctly as this is a service offered by your operator.
Would you be able to share more information about this with me @Luke1931 ? is this regarding a voicemail left on your phone?
Keep in mind that even being something set to your phone this is offered by the network provider.
I have had a look at the O2 Community and found this guide that may help you reset your voicemail pin: https://www.o2.co.uk/help/digital-services/voicemail#:~:text=You%20can%20reset%20your%20PIN,call%209...