They're a bunch of scam artists calling from the DR using magic jack numbers (which explains the bad connection) and the local area code. They pretend to be "DEA" or "FBI" agents. Some could barely speak english. Just ignore it or change your number.
I've received three threatening calls this week from 301-358-0338. I know it's a scam so I just hang up on them and save their threatening calls back to me. I have reported the calls to the DEA and hope the %$#@s get caught. Apparently they are getting up to twenty years in prison for the crime, so turn them in! Save your voicemails and call the DEA. Relax, it's only a scam.