Hmmm…
so this is your CSS:
a.button.add_to_cart_button.ajax_add_to_cart::before {
content: "\f07a";
font-family: 'FontAwesome';
font-size: 15px;
padding: 7px 12px 7px 12px;
color: white;
background: #333;
border-radius: 5px;
}
It adds the icon to the :before
pseudo element.
When you add to Cart woo outputs this :after
pseudo element
.woocommerce #respond input#submit.added::after, .woocommerce a.button.added::after, .woocommerce button.button.added::after, .woocommerce input.button.added::after {
font-family: WooCommerce;
content: "\e017";
margin-left: .53em;
vertical-align: bottom;
}
So a simple option in YOUR CSS would be to change:
a.button.add_to_cart_button.ajax_add_to_cart::before
to
a.button.add_to_cart_button.ajax_add_to_cart::after
That way the icon will get swapped.