i have an iphone 4 and when i try to block calls the person gets my voicemail and i recieve it right away. Is that suppose to happen. If not what do i have to do to fix it so that i can block some one from phoning or messaging me.

I try blocking a number on my iphone 4 and the person was still able to get through. I turned off my phone and took out the sims card put it back in turn my phone back on. I got blocked my friends number got her to call me and she got voicemail and i recieved the voicemail. Apparently im not suppose to . I am trying to block a person overseas that keeps calling me. but they are able to get through how come