Just another typical low-life scamming business that has a robo-dialer to call random numbers to try to scam people who answer. You don't receive voice messages because, when you don't answer and your call goes to voicemail, the bot is already talking; and by the time your VM gets ready to record a message, the bot didn't hear anyone talking and hung up. Answer the call and ask them to stop calling you, or don't answer and block their number. Either way, they aren't any business whom you want to be dealing with. They're scammers.