My mother has this feature (in UK). The first time you call, it will send you to the voicemail and ask you to state who you are. Then she gets a notification an

My mother has this feature (in UK). The first time you call, it will send you to the voicemail and ask you to state who you are. Then she gets a notification and can listen to the message. If she phones you back, the number you are calling from is whitelisted. I think she can press something else to blacklist you, otherwise you stay in the grey zone and will always go to the voicemail. I think she has had a couple of people not leave a message several times and eventually blocked them where she would have been completely happy to speak to them if she only knew who they were..