[Dilettante_Pro]

<style>
.closed { display:none; }
</style>
<div class="obertka">
    <div class="small_cart">
        some code
        <h6>Контакты</h6>
    </div>
    <div class="full_cart closed">
        more some code
    </div>
</div>
<div class="some_parent_lvl1">
    <div class="obertka">
        <div class="small_cart">
            some code
            <h6>Контакты</h6>
        </div>
        <div class="full_cart closed">
            more some code
        </div>
    </div>
    <div class="some_parent">
        <div class="obertka">
            <div class="small_cart">
                some code
                <h6>Контакты</h6>
            </div>
            <div class="full_cart closed">
               more some code
            </div>
        </div>
    </div>
</div>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
<script>
   $('h6').on( "click", function() {
        $('h6').parent().parent().find('.full_cart').addClass('closed');
        $(this).parent().parent().find('.full_cart').removeClass('closed');
    })
</script>