Show dropdowns based on previous dropdown

You need to specify a parent in each child. Carrier:

<label for="carrier_sold">Carrier Sold: </label>
    <select name="carrier_sold" id="carrier_sold">
    <option value="" selected="selected">Select...</option>
    <option value="MetLife">Metlife</option>
    <option value="Travelers">Travelers</option>

    </select>

Travelers: save the parent for each option, for example, in an attribute data-xyz.

<label for="payment_plan">Payment Plan: </label>
<select name="payment_plan" id="payment_plan">
   <option value="" selected="selected">Select...</option>
   <option data-parent="MetLife" value="bill">Bill</option>
   <option data-parent="MetLife" value="full">Full</option>
   <option data-parent="Travelers" value="eft">EFT</option>
   <option data-parent="Travelers" value="rcc">RCC</option>
</select>

jQuery:

$('#carrier_sold').change(function() {
   var parent = $(this).val();
   $('#payment_plan').children().each(function() {
      if($(this).data('parent') != parent) {
                $(this).hide();
      } else    $(this).show();
   });
});

. jQuery , , data-child .

, , . change() vs. blur().