WSClient Play Framework 2.7

I am migrating from Playframework from 2.5 to 2.7. We used to call a Webservice using Writable. Now it is not working with the below syntax.

 // val byteString = ByteString.fromString(temp2)
    .withHttpHeaders(Http.HeaderNames.COOKIE -> s"${sessionCookieName}=${session.get}")
    .execute().onComplete {

Please let know, how could send a post withBody withe below content.

      val content = {
        s"id: ticket/new\nRequestor: $rtUserEmail\n" +
            s"${el._1}: ${
                StringEscapeUtils.unescapeHtml(el._2.replace("\n", "\n ")),

Any pointers and example code would help me fixing this problem,