Call received this morning, which I ignored, as Caller ID was not displayed. Caller did not leave a message.
Wide range of numbers in that exchange registered to BANDWIDTH.COM, a firm offering a wide range of telecom services. As the caller didn't leave voicemail, and didn't identify himself, I decided to block the entire exchange 850-583 on my Andoid phone.
Called several times in a row. I did not answer and they did not leave a message, but I assumed it was on auto-dial due to the frequency of repeat calls.
Caller ID simply ID'd it as "Out of Area". I will probably block because of their persistence and unwillingness to leave a message.