Thats complete horse pucky! Its the oldest excuse in the book to try and get around the real issue. Its been pulled by spammers - it was lame then, its lame now! And guess what, it doesn't work anymore!

Oh, in case you didn't get the memo, the rules have changed which weakens your excuse to useless and worthless..
http://www.tcpalaw.com/
http://www.kleinmoynihan.com/publication/new- ... ctober-16-2013/
http://www.consumer.ftc.gov/articles/0108-national-do-not-call-registry

Which part of ALL the above posts stating they made NO such request wasn't clear to you?

Being on a do not call list doesnt apply to these calls beings they are calling because your number was placed submitted as part of a request for service it falls under the preexisting business relationship part of the do not call acts.

According to Quinstreet.com "Who We Are":

Connecting Customers to You
We have become the leader in vertical marketing and media online by delivering qualified clicks and qualified inquiries at low cost and with great scalability. Our full-service approach and market-leading capabilities enable us to increase your sales while reducing customer acquisition costs by as much as two-thirds.

Don't go to their site without turning off cookies first.

So, block them (if possible) and ensure you're on the Do Not Call registry. If they call again tell them to remove your number from their list, and threaten to report them while also telling them you will file a lawsuit for harassment with the loss of peace of mind.
Or, just don't answer, and DON'T CALL THEM BACK.

Received call twice today with woman who left message that said she was returning a call about an inquiry I made on the internet, which I never did. the call on my cell reads from 714-783-9572, although she said to call 855-494-0971. I am not calling back.

Have been receiving calls at least twice a day from this number.  Women on message said returning a call after I requested it on the Internet.  I do not even know who or what Quinstreet is.

Has called several times last few days and they leave message that states to call and leave them a message.  Very weird.  Have no idea who this is or why they would be calling me.  I have blocked their number from now on.

Has called twice today, "Qunstreet" I do NOT know any Quinstreet, no messages either time. DO NOT CALL LIST!!!!

Rec'd call today, from 855 494-0971, left message on answering machine.  Message from "Quinstreet" stating to talk to us about an inquiry on the internet.  We made no such inquiry.  855 area supposedly from Cambodia