I had the same experience with the beeping calls to my office number. Recognizing that it was a fax machine trying to connect, I forwarded my office phone to our fax line, so the next time it attempted the call, it connected with a fax machine.
The caller is Aetna Insurance--the number reads as Hartford (their HQ) but this one was actually from their Dallas office (I am in the DFW area). I called the sender, informed him of the error (and suggested he correct the fax number they have for the intended recipient--a local nursing home), and shredded the fax (with its HIPAA-protected patient information.
If you get calls from this number, and can forward them to a fax machine, that will end the attempts to make THAT call. It will also provide you with the voice number of the sender so you can request they correct their contacts list.