Australia Post - Price adjustment based on shipping class

functions.php

add_filter( 'wf_australia_post_rate_services', 'alter_service_rate_adjustments', 10, 2 );

function alter_service_rate_adjustments( $rate_service, $rate_code){
	// Array of service codes with combination of shipping class and price adjustment
	$adjustments = array(
		'AUS_PARCEL_REGULAR'	=> array(
									'16' => 4, // Shipping Class ID => Adjustment Price
									'17' => 3,
								),
		'AUS_PARCEL_EXPRESS'	=> array(
									'16' => 20,
									'17' => 21,
								),
	);
	
	$existing_class_ids = array();
	
	foreach( WC()->cart->cart_contents as $key => $values ) {
		$class_id	=	$values[ 'data' ]->get_shipping_class_id();
		if($class_id	&&	!in_array($class_id,	$existing_class_ids)){
			$existing_class_ids[]	=	$class_id;
		}        
    }
	
	if(array_key_exists($rate_code,$adjustments)){
		$class_adjustments	=	$adjustments[$rate_code];
		$adjusted			=	false;
		$adjusted_price		=	0;
		foreach($existing_class_ids as $existing_class_id){
			if(array_key_exists($existing_class_id,$class_adjustments)){
				if($class_adjustments[$existing_class_id]	>	$adjusted_price){
					$adjusted_price	=	$class_adjustments[$existing_class_id];
					$adjusted = true;
				}
			}
		}
		if($adjusted){
			$rate_service['adjustment']	=	$adjusted_price;
		}		
	}
	return $rate_service;
}