Unable to make a call

I am trying to use Cloudlink to make a call. I am unable to make the call. It looks like a simple call, but I am getting a bad request. I am including the C# code I used. I am setting the endpoint is that actual extension. I have never verified if that is correct or if this needs to be in Id of some kind. Any help would be appreciated.

    public static async Task<object> MakeCall(string token)
            // Create an HttpClient instance
            using (var httpClient = new HttpClient())
                // Set headers
                httpClient.DefaultRequestHeaders.Add("Authorization", token);
                Dictionary<string, object> userData = new Dictionary<string, object>();
                userData["to"] = 2214;

                // Serialize the input data
                var f = Newtonsoft.Json.JsonConvert.SerializeObject(userData);
                var jsonContent = new StringContent(f, Encoding.UTF8, "application/json");

                // Make the API call
                var response = await httpClient.PostAsync("https://media.api.mitel.io/2017-09-01/endpoints/2240/calls", jsonContent);

                // Check response status
                if (!response.IsSuccessStatusCode)
                    Console.WriteLine(await response.Content.ReadAsStringAsync());

                // Deserialize the response data
                var responseData = await response.Content.ReadAsStringAsync();
                return responseData;
        catch (Exception ex)
            return null;

What error are you seeing in the exception log?