I looked it up and this number was AOK/legit, actually. Related to a customer service problem I had looked into same day, I just didn't expect it to be from S. San Francisco area code.
Customer service call from 408-606-5271 regarding a purchase I had made through Gift Card Mall earlier the same day. They verified some details (amount of purchase, last 4 of credit card) but did not require any details that seemed out of the ordinary.
I received a call from this number today. CI said "Blackhaawk NTWK. Turned out to be a checky on a gift card I had ordered 15 minutes before. I was extrememly suspicious as they had me repeat all the info on the order like name, last 4 digits on Credit Card ect. I was convinced they were legit and glad they checked it out so fast!