The (305) area code is Miami Florida, where I live. I think that your advise is really stupid. I get calls from (305) every single day and they are not scammers. Don't you think it is bad advise to block the whole area code? What if you live in that area code?
Yes the post you are replying to is over 2 years old, but to answer your question I would block the area code/exchange (in this case block 305-230) combination that is bothering me (assuming the exchange isn't used by someone you would accept a call from). My phone allows me to block as few as 2 digits to as many as 8 digits.