I can only speak for myself. I’d rarely recommend cold-calling an agent.
Agents generally do not answer their own phones. Even if they do, they reserve phone calls for conversations with editors and others at the publishing houses where they either already have deals or hope to make a sale, as well as with their authors and authors they may be courting. They genuinely do not have time to take calls from strangers. This is not because they are mean and unfeeling people. They are simply busy representing the clients they already have, searching for the ones they would like to represent, and doing a vast number of tasks that may not be evident, but that are part of running a business. Because agenting is a business. Publishing is a business.
Many of these calls are fishing expeditions. Writers call and say things like: “I don’t really know how this works, but I thought perhaps you could tell me…”; “I’ve never been published before and I don’t have a clue how to go about it.”; “My book will make you rich. Call me back.” ; “I don’t know if you handle screenplays but I have this amazing screenplay.” What these calls reflect is a lack of preparation and research on the part of the author, and a fundamental lack of understanding about how to approach an agent.
A better approach might be to do as much research as you can about the agent you want to reach out to. Most agents have comprehensive websites that contain specific guidelines about submissions, how they prefer you to communicate with them, the kinds of books that they represent and are searching for. Many have Facebook pages for their agencies. Even if you got the agents name from a website that recommends or lists agents, or a directory of agents, find that agent’s website first. Searching for an agent on Google or another search engine can lead you to an interview with the agent or feature about the agent. These in turn will reveal something about their personalities, taste and inclination. Take time to do the work of understanding who the person is on the other end before you reach out to them. You’ll be better able to position yourself and your work, whether that is through email or letter correspondence. Best of all, laying the groundwork for that initial appeal shows respect for the agent as a professional and reflections your own professionalism.It won’t guarantee a response, but it will increase your chances of getting attention. And isn’t that what you are aiming for anyway?