Update: It looks like it was my fault because I provided my phone number on www.globalspec.com and one of the suppliers whose parts I was looking at must have called me back.

How did these people get my phone number?

A google search of this phone number reveals it belongs to "IQ systems marketing services".  My number is a cell phone, and it is listed on the do not call list, so I shouldn't have gotten this call.  They hung up on my voicemail.