Visual Voicemail not working iPhone 7plus (Verizon unlocked) PrePaid

I currently have an iPhone 7plus that was my moms and is unlocked from the Verizon network.  I am on the prepaid service.  I have been getting calls but no voicemail messages, so I assumed that no one was leaving me any messages at all.  After I received 4 calls from an unknown number, I decided to check the voicemail by calling it because the visual voicemail was not working.  Turns out there were actually a bunch of messages, the last 4 from my doctors with important information.  I tried numerous "fixes" on here and nothing.  I called into tech support and they ended up telling me that because it is a Verizon phone, I cannot get visual voicemail.  After reading some of the posts here, I have seen that some have been able to get their visual voicemail back. 

Can someone please tell me what I should do, what steps to take to get my visual voicemail working?  It is a feature that I feel is based on the phone - NOT AT&T...Please help!