Set Account's Primary Contact as Recipient when creating a new Phone Call

When a new Phone Call is created starting from an Account, the default recipient is the Account itself.
If we want to set the Primary Contact of the Account as Recipient, we need to call the following function inside the OnLoad event of the Phone Call entity.

function ChangePhoneCallRecipientFromAccountToPrimaryContact() {
    // check if is a new phone call
    if (Xrm.Page.ui.getFormType() == 1) {
        // get the Phone Call To Recipient
        var to = Xrm.Page.getAttribute("to").getValue();
        // if the Recipient is an account we continue
        if (to != null && to[0].entityType == "account") {
            // get the account Id
            var accountId = to[0].id;    
            // get the right url for the OData Query
            var serverUrl;
            if (Xrm.Page.context.getClientUrl !== undefined) {
                serverUrl = Xrm.Page.context.getClientUrl();
            } else {
                serverUrl = Xrm.Page.context.getServerUrl();
            }
            // build the request
            var ODataPath = serverUrl + "/XRMServices/2011/OrganizationData.svc"; 
            var accountRequest = new XMLHttpRequest();
            accountRequest.open("GET", ODataPath + "/AccountSet(guid'" + accountId + "')", false); 
            accountRequest.setRequestHeader("Accept", "application/json"); 
            accountRequest.setRequestHeader("Content-Type", "application/json; charset=utf-8");
            // execute the request
            accountRequest.send();
            if (accountRequest.status === 200) {
                var retrievedAccount = JSON.parse(accountRequest.responseText).d;
                // retrieve the primary contact of the account
                var primaryContact = retrievedAccount.PrimaryContactId;
                // if there is a primary contact we set as new To Recipient
                if (primaryContact.Id != null) {
                    var newTo = new Array();
                    newTo[0] = new Object();
                    newTo[0].id = primaryContact.Id;
                    newTo[0].name = primaryContact.Name;
                    newTo[0].entityType = primaryContact.LogicalName;
                    Xrm.Page.getAttribute("to").setValue(newTo);
                }
            }
            else {
                alert("error");
            }
        }
    }
}