how do i post data to a url with its parameters eg

www.sendmessage.com/client/xml/send?client&pass&message&phone

i want to pick the fields client, pass, message and phone from the db and pass them to a function like

def send_msg(entry) do
     {:ok, url} ->
          options = [
            hackney: [basic_auth: {url.client, url.pass}],
            ssl: [verify: :verify_none]]

   {:ok, post_params} = prepare_request_params(entry, url)

      case HTTPoison.post(String.trim(url.url), post_params, headers, options) do

            {:ok, %HTTPoison.Response{status_code: 200, body: body}} ->
                IO.inspect(process_response_body(body))
       end

end

def prepare_request_params(entry, url) do
    {:ok,Poison.encode!(%{
        "username" => "#{url.client}",
        "password" => "#{url.pass}",
        "recipient" =>  ["#{entry.phone}"],
        "message" =>   "#{entry.message}"
    })}
  end