I have someone in my life that leaves useless voicemails all the time and I want something I can do without resorting to legal interaction. I do not want to miss an important voicemail from a prospective employer due to having a missed call during the day and having to deal with the nuisance of going through the call up service.
I can see how that would be annoying, especially if they fill up your voicemails and one that you really need does not get to be left. There is not a way to prevent one number from going to your voicemail. My apologies that I do not have better news for you. You might consider asking that individual to text instead of leaving a voicemail, and explain the need to keep your voicemail clear for business messages.