Who called from 7206067100

They are trying to fax a residential phone.

scam call from 720 606 7100

This number continues to call and try to fax..

Called, voicemail took it.  Message was only a series of beeps as if called from a fax machine.

This was a fax (beeps), going to a residential line.  I tried to call it back (sometimes, companies provide an easy opt-out when you call them back), but this number just was a busy signal when I called it back.

No way to opt-out of this one, that I can see, other than taking the fax and hoping there's some opt-out info on the fax they're trying to transmit.