Error using PHPmailer on live site. Getting warning re: the header redirect: Warning: Cannot modify header information - headers already sent by (output started at... etc.

//THIS THE JQUERY CODE FOR THE TE PICKER YOU CAN IGNORE THIS

<link rel="stylesheet" href="//code.jquery.com/ui/1.10.4/themes/smoothness/jquery-ui.css">
<script src="//code.jquery.com/jquery-1.9.1.js"></script>
<script src="//code.jquery.com/ui/1.10.4/jquery-ui.js"></script>
<link rel="stylesheet" href="/resources/demos/style.css">
<script>
$(function() {
$( "#date" ).datepicker();
});
</script>

<style>
.address{
    display:none !important;    
    }
</style>

//THE REAL CODE STARTS HERE

<?php
//PROCESS THE FORM
if ($_SERVER["REQUEST_METHOD"] == "POST"){
        $name = trim($_POST["name"]);
        $email = trim($_POST["email"]);
        $tel = trim($_POST["tel"]);
        $date = trim($_POST["date"]);
        $message = trim($_POST["message"]);

        if ($name== "" OR $email == "" OR $tel == "" OR $date == ""){
            echo "You left a required field blank! Please fill in ALL the required fields.";
            exit;
            }

            //KILL SPAMMERS
foreach($_POST as $value){
    if(stripos($value,'Content-Type:') !== FALSE){
        echo "You are a spammer";
        exit;
        }

    }
    if ($_POST["address"] !=""){
        echo "You didn't fill in the honey pot. Please try again.";
        exit;
        }

//LOAD PHPMAILER OBJECT
require_once("class.phpmailer.php");
$mail = new PHPMailer();
if($mail ->ValidateAddress($email)){
    echo "Sorry your email did not go through. Please try again.";
    exit;
    }
//END PHPMAILER

//GET THE FORM INFO AND SEND THE EMAIL
        $email_body="";
        $email_body = $email_body . "Name" . $name . "<br>";
        $email_body = $email_body . "Email" . $email . "<br>";
        $email_body = $email_body . "Tel" . $tel . "<br>";
        $email_body = $email_body . "Date" . $date . "<br>";
        $email_body = $email_body . "People" . $people . "<br>";
        $email_body = $email_body . "Message" . $message;

        $email->SetFrom($email, $name);
        $address="info@mysite.com";
        $mail->AddAddress($address, "Contact Message");
        $mail->Subject = "Online Reservation";
        $mail->MsgHTML($email_body);

        if(!$mail->Send()){
            echo "There was an error sending your reservation." . $mail->ErrorInfo;
            exit;
        }

    header("Location: http://mysite.com/testing/contact.php?status=thanks");
        exit;
    }
?>





<?php 
//SUCCESS MESSAGE
if (isset ($_GET["status"]) AND $_GET["status"] == "thanks") { 
?>
<h1>Thanks for contacting us! Talk to you soon...</h1> <?php } else{  ?>




<!--Contact FORM-->
<form method="post" action="contact.php">

<table>
    <tr>
        <th><label for="name">Name / Nombre:</label></th> 
            <td><input type="text" name="name" id="name"></td>
     </tr>

    <tr>     
        <th><label for="email">Email:</label></th> 
            <td><input type="text" name="email" id="email"></td>
    </tr>

    <tr>
        <th><label for="tel">Tel:</label> </th>
            <td><input type="text" name="tel" id="tel"></td>
    </tr>

            <tr class="address">
            <th><label for="address">Address</label></th> 
            <td><input type="text" name="address" id="address"></td>
            </tr>


    <tr>
        <th><label for="date">Date of Reservation? / Fecha?</label> </th>
            <td><input type="text" name="date" id="date"></td>
    </tr>

    <tr>
        <th><label for="people">How many people? / Cuantas personas?</label> </th>
            <td><input type="text" name="people" id="people"></td>
    </tr>

    <tr>
        <th><label for="message">Message / Mensaje:</label> </th>
            <td><textarea name="message" id="message"></textarea></td>
    </tr>

</table>

<input type="submit" value="Send">
</form>
<?php } ?>```