Example of how to remove the summary section from the auth.net accept payment iframe.

authnet_accept_remove_summary.php

<?php // Please do not include the opening PHP tag if you already have one.

add_filter('FHEE__EEG_AuthorizeNet_Accept__getIFrameUrl__request_params', 'tw_ee_getIFrameUrl__request_params');
function tw_ee_getIFrameUrl__request_params($params){
    foreach($params['getHostedPaymentPageRequest']['hostedPaymentSettings']['setting'] as $key => $setting) {
        if($setting['settingName'] === 'hostedPaymentOrderOptions') {
            $params['getHostedPaymentPageRequest']['hostedPaymentSettings']['setting'][$key] = 
                array(
                    'settingName'  => 'hostedPaymentOrderOptions',
                    'settingValue' => json_encode(
                        array(
                            'show'         => false,
                        )
                    )
                );
        }
    }
    return $params;
}