Google claims their users click (organic) search results more often than ads, essentially rebutting the research cited above. A 2012 Google study found that 81% of ad impressions and 66% of ad clicks happen when there is no associated organic search result on the first page.[2] Research has shown that searchers may have a bias against ads, unless the ads are relevant to the searcher's need or intent [3]
Good question, for most directories I use they ask for mobile number to send a message of verification, for the ones which phone you for verification inform the company before hand to tell their customer service people to be ready. I know the bigger the company the more tricky these things get you just have to find out what works best to answer the calls even if they give you a direct number to use. 

Now, it is not that these sites are not interested in Google users. In fact, they have hired us to help them increase their share. However, they are getting so much traffic from sites like Facebook that it seems there is less urgency about attracting this traffic and less willingness to change the site to meet organic standards. Not long ago, sites would urgently and unquestioningly abide by Google’s standards to court that traffic.