I received 3 phone calls from this number, but could not hear anyone. When I attempt to dial the number back, it says the number is disconnected. Weird.

Same here. I called back and got the recorded telephone company message, "The number you dialed is not a working number, Please check the number and try again." How can someone call from a non-working number?

Received a phone call from this number no answer.  When I called back get a recording indicating that the telephone number is incorrect.

Received a call from 305-985-7772 but missed it. Tried calling back and it's a non working number??? So weird a possible hack?

Just received a call with dead air like the other recipients.

This will be a spoofed number for a time wasting tele-marketing company selling stuff we don't want or need who have an auto dialer making nuisance calls but not having enough chancers (sorry agents) to allocate calls to when a poor busy unsuspecting person answers the call.

They spoof the number so as to avoid the "Do Not Call" regulations.  There's a good chance the operators are not even in the US!!

The best course of action is to save them as "Nuisance" in your contacts list and then never answer future calls.