What is going on here?

I went to a provider when I got back to my desk at work I have a voice mail.  There was no actual voice but just a beeping sound.  When I reverse lookup the phone number from the voice mail as well as the providers, it is coming back as from as one address.  My mistake here is that I used a co. cell phone.  But how did they cross reference the land line?  Maybe it is just their screening process but Eliott Spitzer comes to mind.  Am i just being too paranoid?