My supervisor ghosted me
If the professor has a personal administrative assistant, try contacting them and even try scheduling the defense or other meetings through them. I have known professors who rarely respond, but their personal administrative assistants are very responsive and can schedule meetings or otherwise remind them of student deadlines.
If not, try contacting the general administrative staff of the department. The professor might be more likely to listen or pay attention to an email from someone they are familiar with.
Either way, don't be accusatory and try to report bad behavior. Simply say that you are trying to get in contact with this professor and have been unable to reach them through email or phone, that you need to schedule a defense, and ask for their help. They will probably forward your email to the professor; keep contacting the administrative staff every few days if you don't get a response from the professor.