Depends...is there a job opening or are you cold calling? If there is a job opening, apply - the hiring manager doesn't have time to take calls from every potential applicant. If you are cold calling, call, but keep it short - i.e., Hi, I am calling to see if your company is hiring or have plans to hire in the near future? If you get a yes, ask about the application procedure. If no, thank him/her and hang up.