why does my phone go to someones voicemail when they ste no

That's an issue with their carrier or they have do not disturb turned on, not on your side. They will need to work this out.

Possible causes:

• carrier problem on their end
• carrier problem on your end
• They have turned on a focus that limits who can call them.
• They have blocked your number.
• their phone is turned off, in airplane mode, or out of the coverage area .
• They rejected your call because they don’t want to talk to you.