Hi WG1316 👋 welcome back to community! Thank you for posting.
Sorry to hear you have a stuck voicemail notification. If you can please try the following;
1) First, try leaving a new voicemail on the phone. Once done, listen to the new voicemail in full until you are prompted to delete it, (at which point, go ahead and do this.)
2) Check your voicemail inbox is definitely empty by deleting all messages, including any saved ones, and to then perform a reboot of the handset.
Let us know how you get on so we can offer further support if needed! 🌞
Wishing you all the best.
Molly