I'm getting calls from this number and can't call them back it's so annoying and they just hang up when I do answer

Someone calls my cell phone from this number several times a day.  Today, they were calling my work number.  I work in a law office.  When I answered using my lawfirm greeting, they hung up.  I will probably try to call them back from my work phone and see what happens.  I want to irritate them about as much as they irritate me.

Julie, I would advise that your law firm list ALL their numbers on the Do Not Call List. The listing has been PERMANENT now for over 5 years, which means it does not have to be renewed. Once on the DNC List, do some research and report them every time. EVERY Incident is a $10,000 FINE and with the Feds needing money, they will pursue them. It is the only weapon we currently have, so use it as needed.

... you didn't read the part where it said the DNC list wasn't for business numbers.
https://www.consumer.ftc.gov/articles/0108-national-do-not-call-registry