Just to rule out your Mobile phone account and SIM card Can you please as a process of elimination insert your SIM card in another phone and make the call.
If it works fine then I would suggest removing her number from the phone and then re enter it with a slightly different name version
A Samsung Service Centre or Samsung Experience Store will be able to help you too.
Daily Driver > Samsung Galaxy s²³ Ultra 512Gb in Phantom Black.
The advice I offer is my own and does not represent Samsung’s position.
I'm here to help. " This is the way. "
