OK. So in one place you say your husband's phone and in the other you say your son's phone. Obviously it can't be both.
So unless the phones are on the same account as yours, and you have access to the online account for them, you have no way to block another persons phone. Not at least without doing something you shouldn't do and that we can't help you do.
Now, you can just have them put a block on that number on their device (who ever it actually is). They can do that through their contacts. It is extremely simple.