I'm going to ask my mom to change the voice mail greeting from my deceased dad.
Why do you want your mom to change the greeting?
I think my mom is clinging on to the past.
It's wrong to ask your mom to change the voicemail greeting from your deceased dad's greeting because if she wants to remember him that way then it's up to her. The greeting isn't hurting anyone. You shouldn't try to tell your mom what to do because she's an adult and is able to make her own decisions.
She is clinging onto the past and maybe should move on.
Your mom spent significant amount of time of her life with your dad so you need to understand how she must be feeling about your dad. A voice mail greeting of your deceased dad isn't hurting anyone so you shouldn't make a big deal.