On line 14 you have the server validation for telephone:
$WAFV_Errors .= WAValidateRQ((isset($_POST["Telephone"])?$_POST["Telephone"]:"") . "",true,2);
on line 264 you have the input field for telephone number:
<input class="contactText" id="Tel" name="Tel" type="text" value="<?php echo((isset($_GET["invalid"])?ValidatedField("contact","Telephone"):"")); ?>" tabindex="4" title="Please enter your telephone number" placeholder="Telephone" required>
if you update the name of the input field to "Telephone" I think it would all start working properly.