I had the same thing happen, my phone gave the "tone" sound for voicemail and when I checked the phone I had a voice mail.  Dialed it up and got dead silence, nothing!  Thanks for everyone's comments.  I can now delete it without worry.

Have no idea who thye are but they called my cell.he number comes up as a t-mobile unit

i just gogled this phone # today and stumbled across this site. the person saying its a t-mobile # is right this # shows up as my voicemail # and im a t-mobile customer. i live in the burbs outside chicago and was worried about the fact that my cell and voicemail number were totally different. sounds like a router tower for tmobile customers voicemails and who else is listening to them.. big bro. hmmm?

I called my own number and when it went to voicemail I got got "Debra" not a computer and there were no options.  So did three of my contacts to whom I also gave this number.  This number is listed in my phone as the redirect for my voicemail.  I should note that Debra is very polite.  However, "Debra" has no interest in taking messages which is a problem for my contacts.

Do you have T-Mobile? This ius the T-mobile back door voicemail number.