完成当前周期后，PayPal订阅被取消

Question

function change_subscription_status( $profile_id, $action ) {

    $api_username = 'xxxxxxxxxxxxxxxxxxxxxxxxx';
    $api_password = 'xxxxxxxxxxxxxxxxxxx';
    $api_signature = 'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx';

    $api_request = 'USER=' . urlencode( $api_username )
                .  '&PWD=' . urlencode( $api_password )
                .  '&SIGNATURE=' . urlencode( $api_signature )
                .  '&VERSION=76.0'
                .  '&METHOD=ManageRecurringPaymentsProfileStatus'
                .  '&PROFILEID=' . urlencode( $profile_id )
                .  '&ACTION=' . urlencode( $action )
                .  '&NOTE=' . urlencode( 'Profile cancelled at store' );

    $ch = curl_init();
    curl_setopt( $ch, CURLOPT_URL, 'https://api-3t.sandbox.paypal.com/nvp' ); // For live transactions, change to 'https://api-3t.paypal.com/nvp'
    curl_setopt( $ch, CURLOPT_VERBOSE, 1 );

    // Uncomment these to turn off server and peer verification
    curl_setopt( $ch, CURLOPT_SSL_VERIFYPEER, TRUE );
    //curl_setopt( $ch, CURLOPT_SSL_VERIFYHOST, TRUE );
    curl_setopt( $ch, CURLOPT_RETURNTRANSFER, 1 );
    curl_setopt( $ch, CURLOPT_POST, 1 );

    // Set the API parameters for this transaction
    curl_setopt( $ch, CURLOPT_POSTFIELDS, $api_request );

    // Request response from PayPal
    $response = curl_exec( $ch );

    // If no response was received from PayPal there is no point parsing the response
    if( ! $response )
        die( 'Calling PayPal to change_subscription_status failed: ' . curl_error( $ch ) . '(' . curl_errno( $ch ) . ')' );

    curl_close( $ch );

    // An associative array is more usable than a parameter string
    parse_str( $response, $parsed_response );

    echo "<pre>";
    print_r($parsed_response);
    echo "</pre>";

    //return $parsed_response;

}

change_subscription_status( 'I-ASLDBP8A3W1T', 'Cancel' );

此代码立即取消订阅，但是我想在完成当前订阅周期后停止订阅。