Need to block calls to a business

We are a very large company over 1000 people and we are receiving calls from {edited for privacy} trying to reach employees, we have requested the calls to stop as it is against the law to try and harass employees at work.  They hang up and call again and again.  Our security staff continues to tell them not to call.  If we were to have an emergency event and they have our lines tied up we could have a serious situation. 

How do we get these types of calls blocked from MCI World Communications.  Previously we have contact the State Attorney Generals office, but there has to be a way that communication providers can do something about these type of abuses.

Re: Need to block calls to a business
Moderator Emeritus

Have you contacted Verizon about any of the call blocking features?