"called twice but no one answering on the other end. creepy" --- There's nothing "creepy" about it. It's called a "predictive dialer." There's a bunch of scam-- er, agents in a boiler room who answer phones. The predictive dialer dials call out either from a list or in numerical sequence. When it detects that someone has answered a call it made, it connects that call to the next available agent. The time it pauses between calls is based on a statistical estimate that is determined from the number of calls actually answered vs. the number of calls placed, and the length of time it takes for an agent to handle a call.
Sometimes, because it is all so ... well ... statistical, the predictive dialer places a call that is answered, but there is no agent available to take the call. In that case, the call is dropped, and it sounds to you like there is no one on the other end.
The FCC actually has very strict rules regarding the percentage of call that are abandoned like that and how long your line can be seized (I.e., kept from calling out again) by such a hang up. (In the old days, analog phone lines could be kept from dialing out for some time until the calling party released the line. Bad news for emergency services.) But these days, scammers and criminals that use predictive dialers seem to be more prevalent than legitimate or semi-legitimate businesses that use them (whether they actually are or not, I don't know), so you can usually expect far more hang ups than the FCC permits. Hence your problem, which is shared by many others. Don't get creeped out by it.