Cannot set up voicemail

I have an iPhone 8. I started setting up voicemail a while back, but aborted the process and did not complete it. Now, when I try to set it up, it only gives the option to "call voicemail." when do, it says, "I'm sorry, this person hasn't set up their email yet." Or something like that. None of the instructions I've found online work, because my phone will not give the option to "Set Up" voicemail! What do I do?