This number phoned me, I did not recognize it so I did not answer. they hung up and called back immediately.  They got my voicemail 3 times   in the space of one minute and while not leaving a message any of the three times they kept my voicemail recording for 40 seconds each time.  I looked the number up and it comes up as a cell phone on T Mobile.  I do not think this is possible for a cell phone to call as fast as they did and to keep the voicemail engaged while dialing again. This is not a "normal" call.   I suspect it is a commercial company spoofing that number and trying harder than normal to reach the person they called.  I suggest not answering if they call you.