BIN number based discount in WooCommerce

I need to provide BIN number based discount in WooCommerce. I have tried to calculate discount and to apply coupon but none of it works while on the order-pay page. If i go back to checkout it applies the discount. I need this discount to be applied while on the order-pay.

Here is the AJAX POST

                                $.ajax({
                                    type: 'POST',
                                    dataType: 'json',
                                    url: ajaxUrl,
                                    data: {
                                        action: 'apply_coupon_based_on_card_number',
                                        coupon_code: '99vzm2fp' // or whatever
                                    },
                                    success: function(response) {
                                        console.log(response);
                                        if (response.success) {
                                            console.log('Coupon applied successfully:', response.data);

                                            $.ajax({
                                                type: 'POST',
                                                url: wc_checkout_params.ajax_url,
                                                data: {
                                                    action: 'update_order_review',
                                                    payment_method: paymentGateway
                                                },
                                                success: function(updateResponse) {
                                                    console.log('Order review updated successfully.');
                                                    $('.woocommerce-checkout-review-order-table').html(updateResponse.fragments['.woocommerce-checkout-review-order-table']);

                                                    // Append the updated order details
                                                    var orderDetails = `
                                                        <p>Order ID: ${response.data.order_id}</p>
                                                        <p>Subtotal: ${response.data.subtotal}</p>
                                                        <p>Discount: ${response.data.discount}</p>
                                                        <p>Shipping: ${response.data.shipping}</p>
                                                        <p>Total: ${response.data.total}</p>
                                                    `;
                                                    $('.order_details').append(orderDetails);
                                                },
                                                error: function(error) {
                                                    console.error('Error updating order review:', error);
                                                }
                                            });
                                        } else {
                                            console.log('Coupon not applied:', response.data.message);

                                            // Append the order details even if coupon not applied
                                            var orderDetails = `
                                                <p>Order ID: ${response.data.order_id}</p>
                                                <p>Subtotal: ${response.data.subtotal}</p>
                                                <p>Discount: ${response.data.discount}</p>
                                                <p>Shipping: ${response.data.shipping}</p>
                                                <p>Total: ${response.data.total}</p>
                                            `;
                                            $('.order_details').append(orderDetails);
                                        }
                                    },
                                    error: function(xhr, status, error) {
                                        console.error('Error applying coupon:', error);
                                        console.log('XHR:', xhr);
                                        console.log('Status:', status);
                                    }
                                });

and here is the PHP

function apply_coupon_based_on_card_number() {
    // Check if coupon is already applied
    if ( WC()->session->get( 'coupon_applied' ) ) {
        wp_send_json_error([
            'message' => 'Coupon already applied.',
            'order_id' => WC()->session->get('order_awaiting_payment'),
            'subtotal' => WC()->cart->get_subtotal(),
            'discount' => WC()->cart->get_cart_discount_total(),
            'shipping' => WC()->cart->get_shipping_total(),
            'total' => WC()->cart->total,
        ]);
    }

    // Get the coupon code from the request
    $coupon_code = isset($_POST['coupon_code']) ? sanitize_text_field($_POST['coupon_code']) : '';

    // Check if the coupon code exists and apply it
    if ( !empty($coupon_code) && WC()->cart->apply_coupon( $coupon_code ) ) {
        // Mark the coupon as applied in the session
        WC()->session->set( 'coupon_applied', true );

        // Send a success response with the updated cart details
        wp_send_json_success([
            'message' => 'Coupon applied successfully.',
            'order_id' => WC()->session->get('order_awaiting_payment'),
            'subtotal' => WC()->cart->get_subtotal(),
            'discount' => WC()->cart->get_cart_discount_total(),
            'shipping' => WC()->cart->get_shipping_total(),
            'total' => WC()->cart->total,
        ]);
    } else {
        // Send an error response if coupon application fails
        wp_send_json_error([
            'message' => 'Coupon could not be applied.',
            'order_id' => WC()->session->get('order_awaiting_payment'),
            'subtotal' => WC()->cart->get_subtotal(),
            'discount' => WC()->cart->get_cart_discount_total(),
            'shipping' => WC()->cart->get_shipping_total(),
            'total' => WC()->cart->total,
        ]);
    }

    wp_die();
}
add_action( 'wp_ajax_apply_coupon_based_on_card_number', 'apply_coupon_based_on_card_number' );
add_action( 'wp_ajax_nopriv_apply_coupon_based_on_card_number', 'apply_coupon_based_on_card_number' );

Like i said, tried calculating 10% discount also, could not apply it. I keep getting ‘Coupon already applied.’ message but nothing actually happens unless i go back to checkout where coupon shows and only then is applied.