Received 2 calls from this number in the past week, both times they hung up as soon as I answer. When I call back, it does not rung, I just get rapid beeping as if I have been hung up on or disconnected. I'm going to try calling back at an odd time, and hopefully might have better results.
Re: 408-991-9027
That number is Walgreens in Sunnyvale, CA (as of Oct 2008). It is their automated reminder service. For me it was reminding me that I had photographs waiting to be picked up. It might also have been calling you about a prescription or other order.