Calls go directly to voicemail: S-24

A certain phone number (that is in my contacts) goes directly to voicemail whenever they call me....

I have checked (many times) and that number IS  NOT  in the "blocked" calls list...

I have deleted the contact (numerous times) and added again, also with an alias...

This is a Galaxy S24, and the manufacture insists it is an issue with the providers voicemail system..

Thank you for your suggestions...