The number rings busy when you try to call it back.  They call and don't have the courtesy to leave a message.  It can only be interpreted as a bogus call from a telemarketer, survey taker, etc. or other nuisance caller.

Received call from this number about 90 minutes ago (~11:00 AM CDT) on my cell phone. As usual, these TELE-SPAMMERS  do not leave any message.

Suspect it's a SPOOFED NUMBER:
Reverse directory lookup claims the number belongs to:  Gerardo Torres, (on Porzig Pt). Heathrow Florida.

Service Provider: DeltaCom Inc - FL, (1791 O.G. Skinner Dr, West Point, GA, 31833-1759)
Switch Name:ORLFFL42DS2
Provider Type: Competitive Local Exchange Carrier
Phone Line Type: POTS (plain old telephone service)

I answered the call and it was an automated message about a discount Disney trip if I was one of the first 100 respondents. I hung up at that point.

Never call back unless you recognize the number!

If a caller is legitimate, they'll leave a number and a message and they won't keep calling.

If the caller is a scammer, then the number may be spoofed, so if you do reach someone, it may be an innocent party or it might be a non-working number.

If the caller is a scammer and you do get a real phone number, then all you are doing is confirming that they reached a valid number - and they'll sell your number to other scammers.

There is zero benefit to calling back.

Called, I did not recognize phone number. I dont answer any numbers I dont recognize. Did not leave a message. Will not call back.