How to ring someone and go straight to voicemail instead of ringing them?

My phone is a iPhone 4s and his is a iPhone 4, I'm on orange abs he's on 3 (uk)

Put a 5 in between the 086 and other number part… Like this… (08759999999)

The may INTENTIONALLY or inadvertently activated "Call diverts"

Say you do NOT want to be disturbed DND you can change the settings for VM to pick up

if you question is you want to have a conversation then the person who want to end this has to CANCEL All DIVERTS VOICE.,… And when it rings it rings… You know the rest