Will this also block iMessages from a number you want to block?
I know this is an old topic but since it never got answered I wanted to answer it for you.
iMsgs travel through the Apple server and can not be blocked by the VZW call and msg blocking feature. What you can do, is go into the iMsg settings and there should be an option to only receive iMsg's from people in your contacts. This will prevent stranger danger, spam, and the ex-gf/bf from sending you iMsgs.