I was with Bell Telephone when we coined the term "telemarketing" and spent millions to reposition "telephone sales" which at the time was the most hated term in the English language. It worked.
I then started one of the first telemarketing agencies in the US. We did projects for large and small businesses. My articles appeared in the first issues of Telemarketing Magazine, and I spoke at local and national business association meetings.
Bell Labs research and my own experience were the cornerstones for training on this very topic. Main point: put personality in the call. Arthur Godfrey was the first to do this with the radio, his show sold truckloads of Lipton Tea.
When asked why he was so effective, Godfrey said, "I imagine the little old lady sitting in front of her radio in a rocking chair and I speak directly to her." Works on phone, too, as I learned training hundreds of professionals how to do it.