I have no affiliation whatsoever with O2 or any subsidiary companies. Comments posted are entirely of my own opinion. This is not Customer Service so we are unable to help with account specific issues.
Currently using: Pixel 7a (O2 & Lyca), One Plus 6 (Sfr), iPhone 12 Pro Max (Vodafone)
The only way to block people from calling you is on your phone but when you block people I don't think there is a way you can stop them from leaving voicemail messages with out changing your number.