Having problems with my voicemail when I tap the voicemail button it automatically goes to message management system. Then it prompts to enter the number to the voicemail box you want to leave a message when I enter my number it says that mailbox no exsi

When I tap the voicemail button it automatically goes to a message management then prompts u 2 enter the voicemail box you'd want 2 leave a message 4. Or if I'd want 2 access my voicemail box then enter my number. When I enter my number it claims that my number don't exist. I already took it to my carrier & they couldn't fix it & told me to contact apple support since apple has its own voicemail. Been without voicemail 4 2 days now HELP PLZ