If you’re only shipping a product and not using the billing & shipping form fields. You can change the Billing Details text to Shipping Details text by using this function. Shipping Details as the default text makes more sense if you are not using both form fields.
function wc_billing_field_strings( $translated_text, $text, $domain ) {
switch ( $translated_text ) {
case 'Billing details' :
$translated_text = __( 'Shipping Details', 'woocommerce' );
break;
}
return $translated_text;
}
add_filter( 'gettext', 'wc_billing_field_strings', 20, 3 );