Why when I call a certain number it goes straight to voicemail

Why? Because they are not available.

That may mean that they are on a call and do not have call waiting, it may mean that their phone is turned off or out of the service area, it may mean that they have opted to silence unknown callers and the number you are calling from is anonymous or not in their contacts, or it could mean they have blocked your calls.

courtcourt1 wrote:

Why when I call a certain number it goes straight to voicemail

Then let the certain person know.