Visual Voicemail Requiring Password

When I try to open visual voicemail my phone keeps asking for a password just to open it. This is an iPhone X iOS 15.5. It’s a phone my granddaughter uses and there has never been a password set for any part of voicemail and no greeting was ever set up either. When I tried resetting the VVM password thru settings/phone, the “change password button” isn’t even there. This phone was recently wiped and restored from her iCloud and we never set up voicemail on her old phone.