Visual Voicemail not working with Iphone 12 Pro Max switching from Verizon & Android

I am about ready to rip my hair out. Been on the phone with Xfinity all day, and they keep saying it's an Apple issue, but I see other users here who have the same challenges.

I am currently holding for support with Apple but made the Xfinity rep stay on the line since Apple has already told me it's an Xfinity issue.

Here's the rundown:

Visual Voicemail isn't working, no option to set greeting just a box that says "Call Voicemail".  I get a garbled text message from Verizon everytime someone leaves me a voicemail. 

Have reset network settings and cellular data is on. The Level 2 rep that I am working with isn't being very helpful and is arguing with me. Level 3 said to call Apple support. 

Can someone please help me?