Can you go to his office instead? If not ask the receptionist what is going on, obviously he cannot be that busy. Have you tried writing a letter regarding your case? If you do send it certified so they have to sign for it and you know they received it. Keep track of all the ways you have tried to contact him for future reference. If all else fails you can call his office and threaten to file a State Bar Grievance. Perhaps that will get him to take your calls. Failing to communicate on his part is professional misconduct. Good luck.