functions.php

function my_amazon_payments_handler() {
    global $wc_amazon_payments_advanced;

    if ( class_exists( 'WC_Subscriptions_Cart' ) ) {
        if ( WC_Subscriptions_Cart::cart_contains_subscription() || WC_Subscriptions_Cart::cart_contains_subscription_renewal() || ( is_checkout_pay_page() && WC_Subscriptions_Order::order_contains_subscription( $wp->query_vars['order-pay'] ) ) ) {
            remove_action( 'woocommerce_before_cart', array( $wc_amazon_payments_advanced, 'checkout_message' ), 5 );
            remove_action( 'woocommerce_before_checkout_form', array( $wc_amazon_payments_advanced, 'checkout_message' ), 5 );
            remove_action( 'before_woocommerce_pay', array( $wc_amazon_payments_advanced, 'checkout_message' ), 5 );
        }
    }
}

add_action( 'plugins_loaded', 'my_amazon_payments_handler' );