Can’t set up Voicemail on iPhone

So I cannot set up my voicemail and I’ve done lots of researching and trying everything out already. When another phone calls me there is NO voicemail box for them to leave a message. But when I go to try and set it up, there is no voicemail tab under my phone settings, only the option to change the password is there which I have tried that and it just stays on the (saving password) stage and nothing happens, in the actual phone/contact app it only gives me the option to call it, then when I try that it fails to work every time due to my number not having a mailbox set up. Long story short I have no available options to even begin setting up my voicemail and I clearly do not have a voicemail already set up either. I’m running on the iPhone 6s, my software and carrier settings are fully updated as well (yes I even tried resetting my network settings and still nothing)

[Re-Titled by Moderator]