Hi @laurag2
Welcome back to the community
Sorry to hear you're having issues with your grandmothers landline at this time.
How do they have their landline set up? Is it connected to the master socket, extension socket or into the back of the router?
Can you confirm, can they hear the rings at their side or is their just call information on the handset about calls that keep happening with a 'No number' record?
If they can hear the rings, do they have any security cameras or any health equipment plugged into the landline at all?