<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="checkbox" id="isPhoneSelected"/>
<div id="txtPhone" style="display:none">Téléphone est sélectionné</div>
$('#isPhoneSelected').click(function() {
    $("#txtPhone").toggle(this.checked);
});
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